Ukip’s only MP claims he is leaving ‘amicably’, but Nigel Farage accuses him of trying to undermine the party leader

Ukip’s only MP, Douglas Carswell – who defected from the Tories less than three years ago – quit his new party on Saturday accompanied by a burst of acrimonious comment from its grandees. While he insisted he was leaving “amicably” and would become an independent MP without the need for a by-election, the reaction from Ukip leaders past and present suggested Carswell’s exit was anything but harmonious.

Carswell, 45, a leading anti-EU campaigner at Westminster, announced the decision on his blog, saying: “I switched to Ukip because I desperately wanted us to leave the EU. Now we can be certain that that is going to happen, I have decided that I will be leaving Ukip.”

He added: “I will not be switching parties, nor crossing the floor to the Conservatives, so do not need to call a by-election, as I did when switching from the Conservatives to Ukip. I will simply be the member of parliament for Clacton, sitting as an independent. I will leave Ukip amicably, cheerfully and in the knowledge that we won.”

Minutes after the news broke, the current Ukip leader, Paul Nuttall, said the party had not “benefited financially or organisationally from having Douglas in Westminster. With this in mind, his departure will make no difference to my ability or focus on delivering the reforms I promised when elected as leader.”

Nuttall, who failed last month in his bid to enter parliament as MP for Stoke-on-Trent Central, added: “This is not a surprise. I was elected on a pledge to forge unity in the party, and have had many discussions with key players to try to make that happen, but it had become increasingly clear to me that some things were simply beyond reach. Douglas was genuinely committed to Brexit, but was never a comfortable Ukipper.”

Carswell, an anti-EU rightwing libertarian, has always been something of a loner at Westminster, although in recent weeks the Tory whips are known to have been actively courting him at every opportunity, and remain keen to lure him back to the ranks.

With Theresa May holding a slim working majority of just 17 in the House of Commons, a reverse defection would have been a considerable boost.

A long-running feud between former Ukip leader Nigel Farage and Carswell reached new levels of intensity earlier this month over claims that the MP played a role in blocking a knighthood for Farage. Leaked emails showed Carswell joking that Farage should be given an OBE “for services to headline writers”. Yesterday, Farage accused Carswell of trying to undermine him and the current leader at every turn, and of attempting to block his attempt to forge a hard line on immigration policy.

Soon after making his decision, Carswell faced calls to trigger a by-election from Ukip’s biggest financial backer, Arron Banks, a close ally of Farage. The insurance tycoon, who funded the Leave.EU campaign in the referendum and gave £1m to Ukip ahead of the 2015 general election, said earlier this month that he was now concentrating on forming a new political movement.

Andy Wigmore, a spokesman for Banks, said: “The net has been closing in. There is a Ukip National Executive Committee meeting on Monday and he (Carswell) knew he was for the chop, so jumped. He should call a by-election and Arron will stand against him.”

Carswell was re-elected in Clacton at the 2015 general election with a majority of 3,437, beating the Tories into second place. It was a more slender majority than the 12,404 he achieved in the 2014 by-election, sparked by his defection to Ukip.

He has been at the centre of a battle for control of Ukip since Farage departed as leader in July last year, shortly after the UK voted to leave the EU. His decision to leave the party comes just days after Farage accused him of preventing Ukip from becoming a radical anti-immigration party in the wake of the EU referendum.

“The time has now come to have a clean break,” Farage said. “To make sure we don’t have influences like Carswell taking us away from the key arguments like immigration. There have been some in Ukip who want to turn us into a mainstream political party with very bland messages, and I would say Ukip is a radical party or it is nothing.”