David Miliband's leader in this week's New Statesman, which he has guest-edited, is his most significant political intervention since his much-discussed attack on "Reassurance Labour" in the NS earlier this year. In an echo of that piece, the former foreign secretary mounts a critique of "defensive social democracy", an explicit rebuke to those in Labour who believe the party should simply ride the wave of discontent over austerity. He writes:

[I]f defensive social democracy delivers a win - and it is a big if- the problem will be with governing.

Miliband acknowledges that Labour has a bold economic narrative - "that Britain needs fundamental change in its market structure and culture to compete in the modern world." But he is clear that far more detail is needed for the party to convince voters that it represents a credible alternative to the coalition. In a significant overture to the Liberal Democrats, he suggests that the party should take Vince Cable's 2012 Budget submission to George Osborne, lamenting the lack of a "compelling vision" beyond austerity, and "promise to implement it." It is a statement that some in Labour will see as a snub to the shadow chancellor, Ed Balls, who has set out his own five-point plan for growth.

Rather than simply renew commitments to "tax and spend", Miliband writes, Labour needs to make "switch spends". He highlights a proposal by IPPR, the think-tank where he worked before becoming Tony Blair's Head of Policy, to use a ten-year freeze on child benefit to pay for universal affordable childcare. It is a call for Labour to move beyond the dualistic approach of either supporting or opposing the coalition's cuts.

Miliband's fear is that Labour will "confuse being a better opposition with becoming a potential government". His praise for Jon Cruddas, the MP now leading the party's policy review, who Miliband notes is "not a policy wonk - a great advantage", is a sign that he believes Labour will avoid this trap. But his closing assertion that the Labour "cannot be conservative" is a warning to his brother not to appease the party's status quo faction.