Former TV host Robert Kilroy-Silk has withdrawn from the UK Independence Party group of Euro MPs after it discussed kicking him out.
Mr Kilroy-Silk caused uproar in the European Parliament on Wednesday
The East Midlands MEP said he was remaining in the party but would not work with his colleagues in Strasbourg.
He argued he was helping the other UKIP MEPs out of a hole, claiming they had discovered they could not expel him over his criticisms of the leadership.
In a statement, the other MEPs said they "very much regret" his move.
Mr Kilroy-Silk has been vocal about his ambitions to replace current leader Roger Knapman and says UKIP should be a serious political party and not just a pressure group.
As MEPs prepared for their monthly meeting, a UKIP spokesman said the withdrawal of the whip from Mr Kilroy-Silk was "on the cards".
Mr Knapman has repeatedly urged his rival to stop his battle for the leadership, saying he would end up humiliated.
The meeting was branded a "kangaroo court" by Mr Kilroy-Silk, who said he would not be attending.
He said he had been told that MEPs' leader Nigel Farage did not have the votes for withdrawing the whip.
He also stressed that "due process" had not been followed.
Initially he said he did not care if he was ousted.
But later he told BBC News 24: "They needed to dig themselves out of a hole and I have helped them by saying these people in effect have wanted to hang me for the last week or more and now they're suddenly saying 'come and have dinner with us tonight'.
"Well, I don't think I can do that.
"I have said I will not work with the parliamentary party in Strasbourg again but of course I will continue to be a member of UKIP.
"And most importantly I will be doing what I have been doing, which is going round the country trying to put the case for Britain to govern itself and not be governed by Brussels."
He denied suggestions he wanted to set up another party.
Mr Knapman said he regretted Mr Kilroy-Silk's decision, which would halt any leadership ambitions still harboured by the celebrity MEP.
"He did have talents, particularly in the promotion
of the party and of himself. But he has caused us a lot of negative coverage," he said.
"I don't know how he convinced himself we were going to withdraw the whip
"I think the group would have given him a final warning. It is true
that some of his past comments did require some clarification. But he jumped, he
was not pushed."
Conservative co-chairman Liam Fox derided the move as "yet another shambolic episode in the chequered history of UKIP".
Earlier, Mr Kilroy-Silk caused uproar as MEPs discussed the controversy about the proposed appointment of Rocco Buttiglione as a European commissioner.
Laughing, he shouted: "Point of order. Oi! Point of order."
Socialist group leader Martin Schulz accused him of being a hooligan and of "behaving like a spoilt child".
In a point of order, Mr Kilroy-Silk said the European Parliament should not have waited when commission president, Jose Manuel Barroso, arrived late for a hearing on Tuesday.
He wants a vote of no confidence in Mr Barroso, who he argues has treated the parliament with further disdain by producing no proposals on Wednesday.
Mr Barroso has withdrawn his proposed line-up of commissioners, saying more time is needed to find choices which would be approved by MEPs.