As well as presumably being committed to the New Labour policy mix of marketised public services, welfare conditionality and neo-liberal economics, the Purple bookers state their logic that: New Labour is the only governing philosophy to win a general election for two decades.
While this might be true, it is simultaneously true that New Labour - as a 'governing philosophy' - lost the 2010 election. The logic that a political philosophy should be maintained after his failed, simply because it was once successful, is utterly flawed. Thatcherism once rode the high wave of British politics, yet the Tories only became re-electable once they tried to ditch the association.
Importantly, there is a deeper lesson in this for the Labour Party. Throughout post-war history, political parties have consistently been punished for 'ideological hangovers'. For a while in the 1980s, Labour promoted policies which had been roundly defeated at the polls. Similarly, by focusing on traditional Tory themes of Europe and immigration, the post-Blair Conservatives committed themselves to a self-induced electoral wilderness.
While political parties don't win if they commit themselves to old ideas, no matter how successful, nor do they win by marginally repositioning a policy message. Kinnock's defeats in 1987 and 1992 can be seen in this light, as can Cameron's failure to win outright in 2010.
Rather, true success comes when a completely fresh vision and message is offered to the electorate. This doesn't mean dumping on the past, but accepting that history's ideas can't win the battles of the future.
Ed Miliband thus has three options: (a) to take the Progress approach and revive New Labour; (b) to shift away from New Labour and abandon some of its policy proposals; or (c) to offer the public a completely new 'governing philosophy'. While option (a) seems very unlikely, my worry is that we will end up with (b), when what we need is (c).
Of course, developing a new philosophy is not an easy political or intellectual task; the only attempt at it thus far is Blue Labour. Whilst I have written on Blue Labour and am sympathetic to it, it is clear that intellectually it is still disparate, without a totally coherent structure or message. Similarly, it has come across a tide of political opposition within the Labour Party, with many striving to bury it.
Still, it persists in gathering interest and, until I see an equally original proposal of where Labour should go, I think it offers the best hope for winning in 2015. As Chuka Umunna wrote today on Left Foot Forward, Labour has to offer a vision to the electorate. The problem at the moment is that Labour's 'vision' consists solely of a moderately different deficit reduction plan to the Coalition's. This is not the stuff of winning elections.