Ed Miliband has been warned that he can not simply coast to victory at the next election by relying on the unpopularity of the Conservative Party.
In a letter published in The Guardian, leading figures from Labour supporting think-tanks and pressure groups urge Miliband to be bolder.
"If Labour plays the next election safe and hopes to win on the basis of Tory unpopularity, it will not have earned a mandate for such change," the letter warns.
The intervention unites both the left and right of the party against the Labour leader's current strategy - with both the Compass and Progress think-tanks signing up to the letter.
The party intellectuals warn: "Britain faces unprecedented challenges: a financial system still too big to fail or jail; austerity causing unnecessary hardship to those already at the bottom of a massively unequal society; climate change flooding people's homes; and a democratic system that seems pretty irrelevant to any of these problems.
"To begin to tackle these challenges the country needs not just a change of government but a transformative change in direction."
Two polls over the weekend showed Labour and the Tories are now virtually neck and neck in the wake of George Osborne's Budget.
Labour's one point lead over the Conservatives would still result in a majority Labour government in 2015, but the figures have made some Labour MPs jittery.
Labour backbencher Simon Danczuk told the BBC's Westminster Hour last night that Miliband needed to "cut the soundbites" and "talk less to ourselves and more to the wider public". The Rochdale MP said the party should "change tack" and start talking about more than just the public sector.
Shadow business secretary Chuka Umunna said the Labour leadership would not be doing its job properly if all it focused on was day to day polling.
"Polls go up and down, we have seen them fluctuate... what matters is how people vote," he told the BBC One Andrew Marr programme.
"We have seen under Ed Miliband's leadership the Labour party put on over a 1,000 extra councillors, importantly in the marginal seats we need to get a majority at next year's general election.