Douglas Carswell, the only Ukip MP at the last election, is quitting politics in order to “move on to other things” – he said in a statement titled ‘Over And Out’ on Thursday.
The maverick MP (pictured left, with Nigel Farage) – first elected as a Tory 12 years ago – said he had been in the Commons for half of his adult life.
“I look forward to being able to read newspapers without appearing in them,” he said.
Mr Carswell, a long-term Eurosceptic, made the headlines in 2014 when he resigned as MP for Clacton to switch to Ukip, winning the seat back for Nigel Farage’s party.
That move unnerved David Cameron, the then prime minister, who feared an exodus of other backbench Tory MPs – although only one other, Mark Reckless, switched sides.
Mr Carswell then held the seat once again in the general election in May 2015 with a majority of 3,400 or 8 per cent. That made him the party’s only MP after Mr Farage failed to get elected in Thanet South.
Over time, Mr Carswell’s relations with Mr Farage became increasingly strained over issues such as immigration, where he had a more tolerant approach than many Ukip colleagues.
During last year’s referendum he worked with the Tory-dominated Vote Leave campaign, helping it achieve the cross-party support needed for official designation. Most of Ukip, by contrast, were involved with the rival Leave.EU group funded by Arron Banks, an insurance tycoon.
After the surprise victory for the Out campaign, Mr Carswell grew even more distant from Ukip.
He finally resigned in March, suggesting that the party was effectively redundant now that Britain is leaving the European Union. Instead he has been sitting as an independent MP, refusing to impose yet another by-election on his constituents.
“I will leave Ukip amicably, cheerfully and in the knowledge that we won,” he said in a statement that glossed over his often acrimonious relations with the party.
Mr Banks had threatened to stand in Clacton against Mr Carswell at the next election to try to unseat the man he referred to this week as a “dysfunctional old wonky jaw”. The businessman and his allies had promised “guerrilla warfare” to undermine the sitting MP.
Mr Carswell said in his statement that he would be supporting the Conservatives in the June general election.
“I have had great fun working with, and getting to know, many wonderful local people,” he said on his website. “Together, we ran all sorts of local campaigns, from safeguarding local services to getting a new seafront. Local has always come first.”
Mark Reckless, another former Tory MP who joined Ukip in 2014, has also quit – this month – and is now sitting as a de facto Conservative member of the Welsh assembly.
It is believed that Mr Carswell and Mr Reckless both defected from the Tories to try to neutralise the sometimes divisive approach of Mr Farage in pursuing Brexit.