Shadow chancellor Ed Balls has appealed to Business Secretary Vince Cable to work with Labour on a Plan B for the economy.
In an open letter, published in the Sunday Mirror, Mr Balls suggests the two should work together to bring Britain out of recession.
He says he wants to join forces with "sensible people in the Government" - singling out the senior Liberal Democrat and giving renewed backing to the "mansion tax" championed by Mr Cable.
It comes a day after opposition leader Ed Miliband said he was in regular text message contact with the Business Secretary and was "open for business" for joint working in the future.
On Saturday, Deputy Prime Minister Nick Clegg dismissed claims that his party colleague, tipped by some to lead the party into the 2015 election, was being courted by Labour as "ridiculous" and "schoolboy politics".
Mr Balls, in his letter, writes: "No matter how bad things get, David Cameron, George Osborne and Nick Clegg are desperate to cling on to their failing economic plan - putting their political pride above the long-term interests of the country.
"But the country cannot afford to wait until the next election before we get a change of course. Because the longer ministers refuse to act, the more long-term damage will be done to our economy.
"That's why I want to work with other parties - including sensible people in the Government - on a new economic plan. In his heart of hearts ... Vince Cable must know that Plan A is not working.
"After all, before the last election, he warned - with Labour - that David Cameron and George Osborne's policies would backfire.
"And, sadly, our warnings came true. So let's work together on new ideas to create jobs and build our way out of recession."
Meanwhile, two new Conservative ministers who moved into Mr Cable's department in Mr Cameron's reshuffle have called for an end to the "politics of envy" that sought to tax wealth.
In what will be seen as a shot across the bows of Mr Cable, Michael Fallon told The Sunday Telegraph it was vital to "salute" wealth creation "and stop thinking of new ways to tax it".
Mr Fallon said he would champion the scrapping of up to 3,000 regulations, the complete sell-off of the Royal Mail and moves to make it easier to sack underperforming staff.
The installation of Mr Fallon and close George Osborne ally Matthew Hancock under Mr Cable was regarded as a bid to restrain Mr Cable, regarded by some Tories as being anti-business.
Mr Fallon denied that was the case, telling the paper: "I'm not there to keep an eye on Vince Cable, I'm there to keep both eyes on growth."