It's been nine months since the coalition came together in the national interest.
In that time, Nick Clegg and I have discovered we agree on key elements on programmes for national renewal.
From cutting the deficit and restoring responsibility to our finances...
...to getting behind businesses and helping them create more wealth and jobs...
...to redistributing power away from Whitehall to individuals, families and communities.
And we have tried to deliver this agenda in a different way.
Rational debate, not tribal dividing lines.
Reasoned announcements, not headline grabbing statements.
And where there are differences of opinion between us - not rancour but respect.
It's one of those differences that I want to speak about today.
In less than three months, this country will decide whether or not to change our voting system from First Past the Post to the Alternative Vote.
Nick believes we should - and is campaigning for a 'yes' vote.
I profoundly believe we should not - and will campaign for a 'no' vote.
So yes, there is a real difference of opinion between us.
On this one, I don't agree with Nick.
But this is not a source of tension.
And it's not a coalition breaker either.
Far above our beliefs about how the voting system should work, we share a much more important belief - a belief in democracy and the voice of the people being heard.
Once the votes have been cast and once a decision has been made, we will accept the result of this referendum and continue to work together in the national interest.
But now, this country is facing a hugely important, future-deciding vote.
So I'm here today to explain as clearly as I can why AV is completely the wrong reform...
...why it would be bad for our politics...
...and bad for our democracy.
For me there are three big problems with AV.
One - it would lead to outcomes that are unfair.
Two - it is a voting system that is unclear.
And three - it means a political system that is unaccountable.
Let me take each in turn.
First, let me take on this myth that AV is more fair and more proportional than the system we have currently.
This is really important.
Those arguing for AV claim it will make every vote count, end safe seats, encourage smaller parties...
...and that the final result will better reflect the will of the people.
On every measure, that is simply not true.
It won't make every vote count.
The reality is it will make some votes count more than others.
There's an inherent unfairness under AV.
Supporters of unpopular parties end up having their votes counted a number of times...
...potentially deciding the outcome of an election...
...while people who back more popular parties only get one vote.
Because if you vote for a mainstream candidate who is top of the ballot in the first round, your other preferences will never be counted.
But if you vote for a fringe party who gets knocked out, your other preferences will be counted.
In other words, you get another bite of the cherry.
I don't see why voters of the BNP or Monster Raving Loony Party should get their votes counted more times than supporters of the Conservatives or for that matter Labour or Liberal Democrats.
The idea that everyone has an equal voice and an equal vote is deeply enshrined in our existing electoral system
The principle of one person, one vote is what makes our democracy fair.
AV flies in the face of that.
So AV doesn't make every vote count like its supporters say it will...
...and neither will it end safe seats.
Of course, there is an argument that some MPs having ultra-safe seats can create a 'jobs-for-life' mentality and reduce accountability, though they can also be incredibly hard-working.
But AV is not the answer.
At the last election, 225 MPs - one in three - were elected with more than fifty percent outright.
AV would not have made a difference in these places.
And if you look at Australia, where they have AV, nearly half of all seats are considered 'safe'.
What's more, AV will not increase the chances of smaller parties winning a seat.
On the contrary, it could harm them.
Caroline Lucas, the country's first Green Party MP, only got thirty-one percent of the vote in her constituency.
It's the same with the Welsh and Scottish Nationalists.
None of their current MPs got over fifty percent of the votes in their constituencies.
Would these parties be able to hold on to their seats if the threshold was put up to fifty percent?
The evidence from Australia suggests no, where smaller parties have been all but obliterated.
Added to all this, AV is not as proportional as you might think either.
As Roy Jenkins, who chaired the Independent Commission on the Voting System, said: "On its own, AV would be unacceptable because of the danger ... it might increase rather than reduce disproportionality."
The evidence shows that AV would have produced even larger Labour landslides between 1997 and 2005...
...and larger Conservative ones in the 1980s.
Let's just look at one example - 1997.
Back then, the Conservatives won twenty-five percent of seats despite recording thirty-one percent of the vote.
But under AV, we would have been punished further, getting in all likelihood just fifteen percent of seats.
That's even more disproportional.
The simple fact is, AV could exaggerate the inherent biases in the current system...
...giving Labour an even bigger advantage than they already have at General Elections.
The truth is, for all their arguments for change, campaigners for AV really only have one point - that an MP does have to get the theoretical backing of fifty percent of the voters.
But even this is flawed.
The fifty per cent threshold applies to the votes counted - not the number of votes cast in the election.
For example, let's say a voter decides to only mark one preference on their ballot paper - as many end up doing under Alternative Vote.
If the person for whom they cast their vote is eliminated, then this vote is discarded and doesn't count.
The only ones that count are the votes that make it to the final round - from which the fifty percent has to be reached.
So this majority is a complete fix.
It's not so much that the winner has half the electorate behind them...
...as that by virtue of a weird counting system, they have crawled over the finishing line.
And isn't this the point?
This backing is not actual approval. It's passive acceptance.
It can mean someone who's not really wanted by anyone winning an election because they were the least unliked.
It could mean that those who are courageous and brave and may not believe in or say things that everyone agrees with are pushed out of politics...
...and those who are boring and the least controversial limping to victory.
It could mean a Parliament of second choices.
We wouldn't accept this in any other walk of life.
Can you imagine giving the gold medal to someone who finishes third?
No. Of course not.
And we shouldn't accept it with our democracy either.
Second, AV is unclear.
There's a brilliant simplicity to first-past-the-post.
You walk into a polling booth, put a cross against someone's name, drop the paper in a ballot box - and the person who gets the most votes wins.
That goes out the window with AV.
It's not my job to tell you exactly how the system works - that's for the 'yes' campaign to explain.
But even if it was my job, I'll be honest with you, I don't think I could.
Yes, there's a superficial simplicity in getting people to rank candidates in an order of preference...
...and redistributing votes until someone gets fifty percent.
But it's a lot more complicated than that.
Here's a passage from a book detailing how the Alternative Vote system works:
"As the process continues the preferences allocated to the remaining candidates may not be the second choices of those electors whose first-choice candidates have been eliminated. It may be that after three candidates have been eliminated, say, when a fourth candidate is removed from the contest one of the electors who gave her first preference to him gave her second, third and fourth preferences to the three other candidates who have already been eliminated, so her fifth preference is then allocated to one of the remaining candidates."
Do you understand that?
I didn't. And I've read it many times.
And I don't think we should replace a system that everyone gets with one that's only understood by a handful of elites.
This complexity spawns other problems.
It increases the cost of politics.
A whole machinery of bureaucracy will have to be built to explain the system to people.
You can imagine it already.
A quango overseeing the whole process.
Consultants drafted in to construct a message.
Leaflets printed and advertising slots booked.
A monumental waste of time, money and effort.
And quite apart from all this, we may have to buy and install electronic voting machines to make sense of all the different outcomes and possibilities...
...machines which aren't even reliable.
This complexity also leads to uncertainty.
It goes without saying that under AV, it takes longer to count votes - which means weeks can go by before you know who has won and what the government will be.
Last May at our General Election, the country voted on the 6th, we knew the result on the 7th, discussions began later that day and the coalition was formed on the 12th.
In Australia last summer, that whole process took seventeen days.
And it also encourages negative campaigning.
In Australia, voters are lectured at polling stations by party apparatchiks with 'How to Vote' cards.
These cards are the product of number-crunching by party pollsters, telling people the exact order in which to rank each candidate.
That's what politics becomes: people not voting so much in droves, but as drones....
...going into the polling booth with no idea who they are ranking or why.
I don't think the best way of restoring faith in politics is to lumber the public with a confusing system which is more expensive, more uncertain - and leads to them being harangued at polling booths.
Third, and to me most importantly, AV will actually make politics less accountable and make it much harder to kick out governments.
You want to know the best thing about First Past the Post?
It is often decisive - and sometimes ruthlessly so.
It has a habit of rising to the occasion.
Be it 1979. And yes, 1997.
It recognised that the government of the day, had had its day, and it was time get rid of them.
There's nothing more powerful than that - when people see their vote had led to the removal vans driving down Downing Street.
That's real accountability. Real democracy. Real people power.
The problem with AV is that it makes this all the more unlikely.
Hung Parliaments could become commonplace.
Now, it won't surprise you to hear me say that is not necessarily a bad thing and that, as happened last May, it can bring parties together in the national interest.
But let's be clear, when there are more hung Parliaments there will be more haggling and horsetrading between politicians - both before and after elections.
There will be gamesmanship between parties in different constituencies as they try to stitch up second preference votes.
And there could well be an occasion where we have a genuine second-choice government.
If the last election was under AV, there would be the chance, right now, that Gordon Brown would still be Prime Minister.
Ok, the last election was not decisive in terms of who won.
But it was certainly decisive in terms of who lost.
And I think any system that keeps dead governments living on life support is a massive backward step for accountability and trust in our politics.
FIXING OUR BROKEN POLITICS
So for all these reasons, I think AV is the wrong reform.
And I'm not alone.
The truth is that AV is a system that no one actually wants.
No one wants it at home. No one wants it abroad.
In the weeks ahead you're going to hear from a lot of people in the 'yes to AV' camp saying how this is the reform they always called for.
Believe me, they didn't.
One of the board members of the Yes Campaign once said: "I'm sorry but I'm no fan of AV".
The Electoral Reform Society, which is bankrolling the Yes to AV campaign, has called AV a "very modest reform" and said it would not be "suitable for the election of a representative body".
Ben Bradshaw, who is leading Labour's Yes campaign, once said "if one of the reasons that we want reform is to rebuild public trust and confidence in politics, make MPs more accountable, give more power to people...then AV doesn't deliver that".
And last April, even Nick Clegg called it a "miserable little compromise".
The point about AV is that even the people calling for it really want something else...
...whether it's a regional list system or the Single Transferable Vote.
For most of them, it is their fourth, third, or at best second choice.
And, as so often happens in elections using the AV system...
...on May 5th they want their second preference to come first.
When it comes to our democracy, Britain shouldn't have to settle for anyone's second choice.
And this argument that no one really wants it, it's as true abroad as it is at home.
Only three countries use AV for national elections: Fiji, Australia and Papua New Guinea.
In Australia, six in ten voters want to return to the system we have - first past the post.
Indeed, over sixty countries and almost half the world's electors use our voting system.
Are we really going to abandon something that is used around the world for something so obscure and so unpopular?
But let me be clear.
My rejection of AV is not a rejection of reform.
I passionately believe that politics has to change.
It has to change because frankly, in too many ways the political system is broken.
And that's why this coalition is committed to sweeping reform.
We are making votes fairer - by levelling up the size of the constituencies so that every vote weighs the same.
We are making politics cheaper - by cutting the size of Parliament, cutting Ministers' pay and sorting out expenses.
We are making politics - and government - more accountable, by removing the Prime Minister's power to set the date of an election...
...and introducing new rights for constituents to recall MPs who break the rules and new powers for Parliament to oversee the Executive.
But above all, and most importantly, we are putting power directly into the hands of people.
Real transparency - so people know how government works, what it's doing, the results it's getting the money it's spending.
Real engagement - with a new Public Reading Stage for government bills, so people can directly write legislation.
And real empowerment - by devolving decision-making down to mayors, local councils and neighbourhoods, so people call the shots on the things that matter to them, not politicians in Whitehall.
Over the next eleven weeks, the debate over AV is going to heat up right across the country.
But throughout this time, I'll be making my case loud and clearly:
Yes, our politics needs reform.
Yes, we need to shift more power down across the country.
But no to AV.
It means a voting system that is unfair...
...processes that are unclear...
...and politics that is unaccountable.
It is, put simply: the precise opposite of what we need right now.
And that's why I urge the country to vote 'no' in May's referendum.