The former Lib Dem defence minister who lost his job in the recent reshuffle has admitted the party was "naive" in how it dealt with the Conservatives in the first two years of coalition.
Nick Harvey said the party should have taken stronger stance on some issues and was wrong to look quite so happy to be in government with the Tories at the start.
He told a gathering at the Lib Dem conference that despite all the polls pointing to a hung parliament the party had been "incredibly naive" and should have been more prepared for the coalition negotiations.
"The Tories had anticipated and 'endgamed' the coalition negotiations better than we had," he said. "Whatever possessed the negotiation team to say we would abstain?"
During the coalition negotiations the Lib Dems leadership negotiated a deal that would allow it to abstain on a vote on raising tuition fees, but ended up largely voting in favour of the change.
Similarly the party secured the right to abstain on votes on nuclear power and on the married couples' tax allowance.
Harvey said the party leadership failed to take the advice of foreign Liberals who had told them to draw firm red lines on issues and not to ever back down. "If we take public issue with something then capsize on it, we are weak," he said.
Contrary to reports at the time, Harvey explained, rather than being well prepared to hammer out a deal with the Tories, there had actually been "total pandemonium" in the Lib Dem HQ the day after the election once the party realised what had happened.
Harvey's admission runs contrary to the usual line that the Lib Dem's crack negotiation team outmaneuvered the Tories in the days after the 2010 election to secure a good deal for the party.
Nick Clegg's decision to sack Harvey from the government came as a surprise to many, and he told The Huffington Post UK that it was the deputy prime minister's "prerogative" to make such decisions.
"But I'd be less than human if on occasions I entirely agreed with him" he added wryly.
Harvey insisted that despite the errors made since 2010 the party had learned from its mistakes and had made a "huge difference" ensuring the government was "much more civilized" than it would have been had it been a purely Tory one.
The North Devon MP also argued that being in coalition with the Conservatives may have proved to actually be better for the party as it was much easier to differentiate itself than it would have been if there had been a Lib-Lab pact.
Harvey said if that had happened the Lib Dems would have risked being assimilated by Labour and would have been painted by the Tories as simply the "southern branch of the Labour Party".
Looking forward to the next election, Harvey said the party should be prepared to work with either Labour or the Tories but must be careful not to look like it was "for sale to the highest bidder".