The Miliband-Blair war of words is a preview of bigger battles to come

If Labour unity has largely held since the election it is because Miliband has chosen to postpone almost all policy decisions.

Tony Blair's dramatic intervention in the centenary edition of the New Statesman (180 pages, out now) leads several of today's papers (the Independent and the Times have splashed on it), with some of the former prime minister's key allies taking the opportunity to air their own concerns about the party's direction under Ed Miliband. The increasingly outspoken Peter Mandelson tells the Independent: "Tony is saying what he has always thought – that the old dividing lines between the uncaring Conservative cuts and Labour spending has got to be redrawn for new times.

"I suspect the two Eds realise this. Their call for One Nation is the right starting point, but there are major structural challenges and choices facing Britain and Labour must consider the difficult changes and reforms needed to address them."

Alan Milburn, Blair's former health secretary, adds: "The closer the election comes, people will stop asking Labour what it is against. They will want to know what Labour is for and what, if elected, it would do. Tony Blair is right to argue that the sooner that process begins in earnest, the better."

One suspects that Miliband, who wasted no time in shrugging off Blair's warning not to "tack left on tax and spending", will be unfazed by their words. Both Mandelson and Milburn are no longer MPs, of course, and have little sway over today's Parliamentary Labour Party. But Blair's intervention and the response to it offers a preview of bigger battles to come. It's often said that Labour is more united now than at any point in recent history but this ignores the fact that there's been little to be disunited about.

Miliband's "blank sheet of paper" is gradually being filled but the Labour leader has chosen to postpone almost all policy decisions until 2014-15. Even when he proposes a new measure such as the reinstatement of the 10p tax rate, or the introduction of a "mansion tax", Miliband is careful to emphasise that these are examples of what Labour would be doing were it in power now, not manifesto commitments. The same applies to the party's five point plan for jobs and growth, the 50p tax rate, benefits uprating and just about every policy area Miliband has touched on since becoming leader.

But at some point before the election, he will need to decide where he really stands. Will Labour, for instance, pledge to stick to the coalition's spending limits for the early years of the new parliament (as Labour did with the Tories' in 1997) our outline its own alternative plan? What will the balance of tax rises to spending cuts be? Will he propose cuts to the welfare budget or allow the burden to fall entirely on public services? Will he pledge to keep Michael Gove's "free schools"? How far will he go in reversing the coalition's NHS reforms? Will he retain the £26,000 benefit cap? 

Liberated from office, Blair enjoys the luxury of posing questions without answering them (although NS editor Jason Cowley has a go in today's Times) but Miliband does not. And once he begins to set out his stall, Labour unity could quickly begin to fray. Recall the tumult that followed Ed Balls's declaration of support for the public sector pay freeze and Labour's decision to abstain on the workfare bill (a move that prompted a rebellion by 44 backbenchers). As one Labour MP recently told me, a pledge to make further cuts to public spending (as the party will surely do) would make such rows "look like a tea party". For this reason, among others, David Cameron and George Osborne will continue to appear unreasonably cheerful. Most of their tough decisions are behind them; Labour’s are all still to come.

Tony Blair talks with Ed Miliband during a Loyal Address service to mark the Queen's Diamond Jubilee at Westminster Hall. Photograph: Getty Images.

George Eaton is political editor of the New Statesman.

How Jim Murphy's mistake cost Labour - and helped make Ruth Davidson

Scottish Labour's former leader's great mistake was to run away from Labour's Scottish referendum, not on it.

The strange revival of Conservative Scotland? Another poll from north of the border, this time from the Times and YouGov, shows the Tories experiencing a revival in Scotland, up to 28 per cent of the vote, enough to net seven extra seats from the SNP.

Adding to the Nationalists’ misery, according to the same poll, they would lose East Dunbartonshire to the Liberal Democrats, reducing their strength in the Commons to a still-formidable 47 seats.

It could be worse than the polls suggest, however. In the elections to the Scottish Parliament last year, parties which backed a No vote in the referendum did better in the first-past-the-post seats than the polls would have suggested – thanks to tactical voting by No voters, who backed whichever party had the best chance of beating the SNP.

The strategic insight of Ruth Davidson, the Conservative leader in Scotland, was to to recast her party as the loudest defender of the Union between Scotland and the rest of the United Kingdom. She has absorbed large chunks of that vote from the Liberal Democrats and Labour, but, paradoxically, at the Holyrood elections at least, the “Unionist coalition” she assembled helped those parties even though it cost the vote share.

The big thing to watch is not just where the parties of the Union make gains, but where they successfully form strong second-places against whoever the strongest pro-Union party is.

Davidson’s popularity and eye for a good photo opportunity – which came first is an interesting question – mean that the natural benefactor in most places will likely be the Tories.

But it could have been very different. The first politician to hit successfully upon the “last defender of the Union” routine was Ian Murray, the last Labour MP in Scotland, who squeezed both the  Liberal Democrat and Conservative vote in his seat of Edinburgh South.

His then-leader in Scotland, Jim Murphy, had a different idea. He fought the election in 2015 to the SNP’s left, with the slogan of “Whether you’re Yes, or No, the Tories have got to go”.  There were a couple of problems with that approach, as one  former staffer put it: “Firstly, the SNP weren’t going to put the Tories in, and everyone knew it. Secondly, no-one but us wanted to move on [from the referendum]”.

Then again under different leadership, this time under Kezia Dugdale, Scottish Labour once again fought a campaign explicitly to the left of the SNP, promising to increase taxation to blunt cuts devolved from Westminster, and an agnostic position on the referendum. Dugdale said she’d be open to voting to leave the United Kingdom if Britain left the European Union. Senior Scottish Labour figures flirted with the idea that the party might be neutral in a forthcoming election. Once again, the party tried to move on – but no-one else wanted to move on.

How different things might be if instead of running away from their referendum campaign, Jim Murphy had run towards it in 2015. 

Stephen Bush is special correspondent at the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to British politics.

0800 7318496