One of Vince Cable's closest allies has raised the prospect of a change of leadership for the Liberal Democrats.
Michael Oakeshott's comments came a day after Nick Clegg launched his latest attempt to distinguish his party from the Conservatives with proposals for a new tax against the wealthiest.
The deputy prime minister's suggestion in an interview with the Guardian did not come with any real details and was quickly rejected by chancellor George Osborne.
"We have lost over half our market share, if you like, since the election," Oakeshott, a Lib Dem peer, told the Today programme.
"Any business that had done that would be looking very hard now at both its strategy and its management to see how we get some of that back - because otherwise we're going to lose a large number of seats at the next election."
He added: "If you're Sainsbury's you would look very hard both at what's happened to the brand, and why.
"We have good policies which are popular, but on things like the banks, sorting them out, we have to fight very hard not just to put the message across but to get it implemented in government."
In a sign that the Lib Dems were prepared to fight for the measure, by the evening it emerged the party were looking at a 0.5% tax on the assets of the wealthy. An 'accessions tax' on those receiving estates is also under consideration, the Guardian newspaper reported.
Oakeshott warned that 39 out of the Liberal Democrats' 57 MPs had held their seats against Conservative opponents only with the help of significant numbers of Labour voters.
He warned they would all become vulnerable in 2015 if nothing is done quickly to win over support from Labour's tactical voters.
"If we don't get some of those back we are going to lose far more seats than we need to at the next general election," he added.
Cable, the business secretary, made clear earlier this summer that he was prepared to lead his party at some stage in the future.
That sparked a flurry of speculation about Clegg's departure after the 2015 general election - and raised the likelihood that he might be ousted before the poll, in a bid to limit the damage of five years in government with the Conservatives.