There are rare moments in the Commons when principle and politics come together. One of these will happen tomorrow evening (Wednesday) when eurosceptic Conservative MPs join with Labour in voting in favour of a real-terms cut in the EU budget. An alliance, at first sight against nature, is taking shape between pro-EU Labour MPs and anti-EU Conservative ones. Tory MP Douglas Carswell, who says that Britain’s membership of the EU is like "being shackled to a corpse", will vote in the same lobby as me, a passionate, unashamed believer that European integration has been good for my country.

The first task of any parliament, anywhere in the world, is to vote money. To vote against a budget proposed by a Conservative government is not as unpatriotic action by Labour, anymore than George Osborne was inspired by anti-British beliefs when he savaged Gordon Brown’s budgets.

All Labour MPs will do on Wednesday is fall in behind Labour MEPs, who also voted against the seven-year EU budget last week in the European Parliament. The reason is simple. The budget or or Multiannual Financial Framework (MFF) as it is known in eurospeak is a product of the poorest, most unimaginative EU governance seen since the Treaty of Rome in 1957. It is a budget which continues in the more-of-the-same tramlines that have led Europe, under the controlling conservative majority in the Commission and Parliament, incarnated by the two centre-right politicians, José Manuel Barroso and Herman Van Rompuy, to its present stagnant state. There is nothing in the MFF for growth, for jobs, for the green economy or any measures to restore the confidence of European citizens that the EU is a project which has social justice and a reduction of greed and growing inequalities at its heart.

It is the re-entry of politics into the European debate that is long overdue. To be pro-European is not to endorse each and every proposal of the Brussels apparat. Some months ago, I coined the term "Brexit" – to describe the growing British politics of pushing open the exit door to the EU. Endorsing a bad Brussels budget will accelerate Brexit, as a governing party that is divided against itself between soft and hard Eurosceptics will not long stand.

There are two kinds of political discussion on the EU. The first is whether we should be in the EU at all. The second is what kind of EU we want. It is unclear how many Tories now think, like Ukip, that Britain would be better off out. Against such Brexitites are those, mainly Labour and Liberal Democrat MPs, who want the UK to stay in and be a player in seeking a better, more focused Europe.

Continuing the same old budget spend on protectionist agro-industry subsidies will suit the big landowners like the Queen and the Cooperative Movement, which are the principal beneficiaries of the Common Agricultural Policy in Britain. Subsidising EU cows when millions of human are out of work makes no sense. In the 1990s, income in south Yorkshire had fallen so low that the region, where I am an MP, became eligible for EU help and £700m arrived from EU taxpayers to help.

As prime minister, Margaret Thatcher increased the UK contribution to the-then European Community budget from £654m in 1984 to £2.4bn in 1990, thus providing Jacques Delors with the money to shape the single market. We should be spending more in Poland, Bulgaria and Romania, so that those nations can grow and keep more of their citizens working at home, rather than being economic migrants elsewhere in Europe.

But the MFF does none of these things. Conservative MPs who want out of Europe will vote against the MFF on Wednesday. Labour MPs who want to stay in a Europe which changes its priorities will do likewise. Meanwhile, David Cameron and William Hague, who have spent the last fifteen years telling voters Europe was a bad thing, are now approaching a moment of truth. Are they for Brexit or are they for Europe, but a Europe that rejects austerity and social dumping,  increases common rules on justice, and speaks with one voice globally? So far, the government has tried to be half-in, but not fully supportive of the EU. Time is running out. The vote on Wednesday will lift still further the curtain on the biggest choice facing Britain in generations.

Denis MacShane is Labour MP for Rotherham and a former Europe minister