Nick Clegg backed by Cable in Lib Dem leadership row
Senior Lib Dems have rallied round Nick Clegg after calls from some in the party for him to stand down as leader.
Business Secretary Vince Cable and former leader Sir Menzies Campbell said such attacks were to be expected at this stage in the Parliament.
Mr Cable said the deputy prime minister was "sufficiently resilient to ride through this".
The attacks were led by Lord Smith of Clifton who said Mr Cable should lead the party into the next election.
In an interview with BBC Radio 5 live's Stephen Nolan on Saturday evening, the Lib Dem peer said Mr Clegg had "done nothing in the last two years" and the party's poll ratings were "desperate" as a result.
"If we put Vince Cable in we'll have our poll rating soar because he is economically literate - unlike Nick Clegg. And he is clearly a leader of the future. We don't need all these young kids running the government."
He added: "I think (Mr Clegg) loves the ministerial limousines, he's a cork on the waves, he has no strategic view whatsoever."
Lord Smith returned to his attack on Sunday, telling the BBC News channel he was "articulating the views of many in the party".
He claimed that the party was losing members "faster than the pubs are closing" and that if action was not taken soon it would return to the days when it had just five MPs.
"We have got to try and do something to staunch the haemorrhaging of our support," he said, adding that Mr Cable, as an older and more experienced figure, should take over as leader.
BBC political correspondent Chris Mason said while Lord Smith was a long-standing Liberal Democrat and a former professor of politics, he was not a big name within the parliamentary party.
Nonetheless, his critique of Nick Clegg was "striking because of its venom", he said.
Lord Smith was joined in his attack by Adrian Sanders, Lib Dem MP for Torbay, Mr Clegg must stop "just bumbling along worrying about the future" and that he needed to "surround himself with winners".
Andrew Bridgwater, vice-chairman of Devon and Cornwall regional party and chairman of the Lib Dem education association, also called on Mr Clegg to resign.
"The sooner Nick resigns and creates a vacancy for Vince, the better," he told the Independent on Sunday.
"To put it bluntly, I would encourage Vince Cable to stand for the leadership to take us into the next election."
Lib Dem Treasury spokesman Lord Oakeshott last week became the first party figure to call publicly for Mr Clegg to consider his position - but he was quickly rebuffed by former leader Lord Ashdown.
Now Mr Cable, who briefly led the Lib Dems in a caretaker role before Mr Clegg's election and has not ruled out a return to the top job at some stage, has rallied behind Mr Clegg.
"I don't give any time to these personal criticisms of Nick Clegg that are being made at the moment," he told BBC Radio 4's The World This Weekend.
"It's inevitable in the mid-term of Parliament when parties' popularities wane, when difficult decisions are being made, that some of the activist base will attack the leadership.
"That's happened many times before. The Tories are doing it. David Cameron has come under a lot fire in the last few weeks. Nick Clegg has got the same but he is sufficiently resilient to ride through this, I think."
Mr Cable denied the party was facing wipeout at the next election and insisted its current poll ratings, of about 15%, were not as bad as they had been in the past and that the party could recover support through hard work at a grassroots level.
Sir Menzies Campbell also rejected claims Mr Clegg was "bumbling along" as party leader insisting he was in "full control".
"Of course it is September and it wouldn't be September if there wasn't speculation about the leadership... it's the sort of thing you get in the run-up to the party political conferences."