Simon Hughes, the deputy leader of the Liberal Democrats, has said that a power-sharing deal between his party and Labour could happen as soon as 2015.
The bisexual MP added that his party’s MPs should be able to veto coalition coalition policies.
The Tory/Lib Dem coalition government marked its first 100 days in power this week but Mr Hughes said that a deal with Labour was still “on the agenda” and indicated it could take place by the next general election.
He told BBC Radio 4’s Today programme: “The idea of a centre left, of a progressive liberal Britain, is still very much for me what I am here to achieve.
“Who knows, there may be a coalition with a Labour party if they are progressive at the next election, after the next election or sometime in the future. It’s on the agenda.”
The MP was understood to be against the coalition and preferred the idea of a deal with Labour in May.
Mr Hughes added that Liberal Democrat MPs should be able to veto coalition policies.
“If you want a coalition to deliver the vote then you have to make sure everybody has bought into that,” he said.
“It’s a matter of practical politics, the answer is therefore: yes, the parliamentary party, on behalf of the wider party, on big issues has to say, ‘No, we can’t go down this road.'”
At the weekend, Mr Hughes, who is not a government minister, said there would be no pact with the Conservative Party at the next general election and said that his party would field candidates against the Conservatives.
Government figures have been unwilling to comment on the future of the coalition.
Reports say discontent is growing in the Liberal Democrat party over the coalition’s programme of cuts and polls suggest the party is losing popularity.
A recent Guardian/ICM poll put the Liberal Democrats on 18 per cent, down on six since the election. Labour and the Conservative Party were both on 37 per cent.
Last month, Mr Hughes said that the government will give gay couples the right to civil marriage.
He predicted that the change would be made before the next general election.