Pressure is mounting on Nick Clegg amid fresh warnings from Liberal Democrats over his leadership of the party.
Senior party figures have warned that the Deputy Prime Minister is not "indispensable" and could be replaced by Business Secretary Vince Cable.
Adrian Sanders, a veteran Lib Dem MP, told The Sunday Times that Mr Clegg needed to stop "just bumbling along worrying about the future" and to take action to rebuild support in the party.
His comments were echoed by the Lib Dem peer, Lord Smith of Clifton, a former professor of politics, who told the paper that Mr Clegg was "just a cork bobbing on the waves" with "no strategic vision at all".
"It's not as if Clegg is indispensable. Vince Cable possesses the appeal and the credibility to lead the Liberal Democrats into the next election," he was quoted as saying.
Andrew Bridgwater, vice-chairman of Devon and Cornwall regional party and chairman of the Lib Dem education association, went even further, calling on Mr Clegg to go.
"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."
Their comment came after one of Mr Cable's closest allies, Lord Oakeshott of Seagrove Bay, warned last week that the party may have to consider a change of "management and strategy" if it was to stand any chance at the next general election.