Chris Huhne, the former Liberal Democrat Cabinet minister, has said his party and Labour could form a "historic radical coalition" after the 2015 general election.
Mr Huhne dismissed speculation that Nick Clegg would not be able to forge a partnership with Labour in a hung parliament after serving as Deputy Prime Minister under David Cameron. Ed Miliband has said it would be "difficult" to form a coalition with Mr Clegg but not entirely ruled out the prospect.
The former Energy Secretary, who was given an eight-month prison sentence for perverting the course of justice after asking his former wife to take his penalty points for speeding, said there was "common ground" between the Lib Dems and Labour on housing, more green taxes, raising the personal tax allowance beyond £10,000 and foreign policy, particularly Europe.
Writing in Juncture, the journal of the IPPR think tank, Mr Huhne said: "The assumption that Nick Clegg, having consolidated a centre-right hold on the Lib Dems, is preparing to deal with the Tories next time is wrong. He is certainly safer as leader than he looked a year ago. Vince Cable did not have a good [party] conference [in September]. But it is Nick who has been making clear overtures to the left of the party."
He added: "The DNA of the Liberal Democrats is anti-Conservative…Labour and the Lib Dems' narratives on the economy are going to be fundamentally different in the run-up to the general election, but that is not fatal. It will disguise a potential common agenda around lifting living standards and reducing inequality not just of opportunity but also outcomes, which matters to the Lib Dem left."
Many Lib Dems are keen to keep open the option of a deal with Labour. Some fear that their party would be seen as an arm of the Tories if it were to form a second coalition with Mr Cameron's party. But they accept that Mr Clegg would have to be guided by the election result-and talk first to the party which won the most seats.
Mr Huhne, who was part of the Lib Dem team which negotiated with both main parties after the 2010 election, said a coalition with Labour was on the cards next time "as long as the votes fall the right way." Revealingly, he said: "As soon as it looks as if the party can only deal with one of its potential partners, its bargaining position in any negotiation is fatally weakened."