Liberal Democrat peer Lord Oakeshott has quit the party following a botched attempt to oust Nick Clegg as leader.
Oakeshott, a close ally of Vince Cable, said on early Wednesday afternoon that he was leaving the party with a "heavy heart". In a statement he insisted that he was right to call for Clegg to go but acknowledged his methods may have damaged those who shared that view.
He said under Clegg's leadership the Lib Dems appeared to have "no roots, no principles and no values" and were in deep trouble.
"I am sure the Party is heading for disaster if it keeps Nick Clegg; and I must not get in the way of the many brave Liberal Democrats fighting for change," he said.
Oakeshott also said he was sorry to have "so upset and embarrassed my old friend Vince Cable". As Clegg faced pressure to resign following poor election results, the business secretary attacked Oakeshott's actions as "totally inexcusable".
On Tuesday, The Guardian published the results of a survey conducted by ICM and commissioned by Oakeshott which suggested Clegg was on track to lose his seat at next year's general election. The poll also suggested Lib Dem MPs could be more likely to survive if Clegg was replaced.
In his parting shot, Oakeshott also published polling data that suggested Lib Dem chief secretary to the Treasury Danny Alexander was heading for a heavy defeat in his Scottish constituency in 2015.
Allies of the deputy prime minister viewed the timing of the leaked poll as a deliberate attempt to undermine Clegg by a long time critic.
Earlier on Wednesday, Clegg warned Oakeshott he would take "appropriate steps" against him, suggesting he would be expelled from the party.
The Lib Dem leader said it was "unacceptable" for the peer to have sought to destabilise his leadership in the wake of poor local and European election results by commissioning a poll on the party's general election chances and then leaking it to the press.
Clegg said: "I think it is wholly unacceptable for people in a campaigning political party, facing very, very difficult elections last week, as we were, to find out now with hindsight a senior member of the party, far from going out and trying to win votes, was spending money and time seeking to undermine the fortunes of the party.
"Obviously parliament will resume next week. A lot of these things will be taken up then and discussed, in the House of Lords and the House of Commons, and following those discussions appropriate steps will no doubt be taken."
Clegg also said the ICM poll had also been "confounded by the actual election results" which showed an increase in support for the party in Sheffield. "I don't need some partial poll to tell me how people actually voted in my constituency," he said.
Cable, who is in China on a government trip, had moved to distance himself from Oakeshott amid suggestions he was pulling the strings in an attempt to secure the leadership for himself.
In a strongly worded statement, the business secretary said his friend's actions had been "totally inexcusable and unacceptable".
"I have made it very clear repeatedly that he does not speak or act for me," he said. "Commissioning and publishing polls without the consent of the Member of Parliament, as in the case of Sheffield Hallam, is utterly reprehensible."
"There are undoubtedly raw feelings in the wake of poor local and European election results. We need to respond in a measured way. Public speculation about the leadership is an unwelcome distraction and as I made absolutely clear yesterday there is no leadership issue as far as I'm concerned."