Sir Menzies Campbell's position as Lib Dem leader is "under discussion", his deputy Vincent Cable has told the BBC.
Sir Menzies has said he wants to lead the party into the next election
But Mr Cable said he did not think Sir Menzies' job was under threat, despite some in the party wanting him to go.
He urged the party not to panic over recent poor opinion polls in what was currently an "extremely febrile and volatile" political environment.
A senior Liberal Democrat has told the BBC that an announcement is expected about the leadership imminently.
There was much speculation at the party's conference last month - at a time when an autumn election was expected - about who would succeed Sir Menzies.
That speculation was welcomed by Sir Menzies as a sign there were talented "young turks" in the party.
But he insisted that he would stick to his pledge to lead the party "into the next election and beyond", telling members he was not too old at 66 to lead the party.
However, since Mr Brown all but ruled out an election until at least 2009, some Lib Dems believe they need to act to replace their leader now.
That talk appears to have been prompted by poor opinion poll results - the latest being an ICM poll in the Sunday Telegraph which suggested Conservative support at 43% with Labour on 36% and the Lib Dems on 14%.
Lib Dem peer Lord Taverne told BBC Radio 4's World at One programme that he had great respect for Sir Menzies, but he was the "wrong person for the moment" and should step down within weeks.
'Read the runes'
"When you talk to people privately there's absolutely no doubt that the overwhelming number of peers want a change [of leader]," he said.
"I can't claim to be a representative member of the party, let's be absolutely clear about that. But my general impression is quite clear, if there's not a change of leadership, the party goes down the drain."
And Sir Chris Clarke, the party's former leader at the Local Government Association, said Sir Menzies had done a "fantastic job" as foreign affairs spokesman, but different skills were needed for the leadership.
He warned Sir Menzies: "Read the runes, go with dignity, go with the respect that you have, go back into the job you've been doing so well [on foreign affairs]."
But the party's deputy leader, Vincent Cable, told the BBC it would be "absolutely foolish" to rush into a decision about the leadership when the polls were so volatile.
Asked whether he thought Sir Menzies' post was under threat, Mr Cable said: "It's certainly under discussion. But I don't think it's under threat and I think the key point for all our activists and MPs and lords is that we shouldn't panic in what is a very volatile political environment."
He added: "I remember in the middle of our party conference, which was only a few weeks ago, our leader was being shown in some polls to be more popular than David Cameron. Brown was ruling the roost: he was the hero of the hour - he's now the 'zero'."
Sir Menzies became leader early in 2006 after the party's most electorally successful leader for 80 years, Charles Kennedy, was forced out after a rebellion by members of his front bench team.
Sir Menzies has always said he will fight the next election, with most commentators believing he will then step down shortly afterwards.
He appeared to confirm this during the Lib Dem conference by saying he was giving talented young Lib Dems the chance to show what they could do.
Among those likely contenders is Chris Huhne, one of those Sir Menzies defeated for the leadership, and Nick Clegg, who told the Lib Dem conference he wanted to succeed Sir Menzies.