Liberal Democrat MPs should get a veto on policies from the coalition Government, the party's deputy leader has claimed.
Simon Hughes said his party should be able to tell the Conservatives: "No, we can't go down this road."
He also indicated that a partnership between the Lib Dems and Labour was still possible, as early as the next general election.
Mr Hughes told the BBC: "If the coalition wants to deliver (parliamentary) votes, neither party on its own has a majority, so we have to make sure everyone is brought into that. As a matter of practical politics... the parliamentary party, on behalf of the wider party on big issues, has to be able to say, 'No, we can't go down this road'."
He added that a coalition between Labour and his party was still "on the agenda", perhaps by the time of the next general election in 2015.
His comments come amid falling poll ratings for the Lib Dems and concern among rank-and-file members over some of the policies being pursued by the coalition.
Mr Hughes, who is not a government minister, is on the left of the Lib Dems and is thought to have favoured a deal with Labour in the aftermath of the election in May.
Last weekend he ruled out any pact with the Conservatives at the next general election.
Mr Hughes rejected suggestions that they could agree not to run candidates against each other in seats which were clearly winnable for one or other of the parties.