Maverick Tory Douglas Carswell has defected to UKIP and quit as MP for Clacton, saying he will contest the subsequent by-election for Nigel Farage’s party, BBC reported.
If he wins the support of voters he will be the first elected UK Independence Party MP in the Commons.
The Eurosceptic backbencher said he wanted to “shake up” the cosy Westminster “clique”.
Mr Carswell added he did not believe Prime Minister David Cameron was “serious about the change we need”.
The surprise announcement was made at a press conference in central London.
Mr Carswell said the decision to jump ship from the Conservatives had given him “sleepless nights” but he wanted to see “fundamental change in British politics” and UKIP – a party he believed belonged to its members rather than a “little clique” of political insiders – could deliver it.
“This hasn’t been an easy decision. I have been a member of the Conservative Party all my adult life. It’s full of wonderful people who want the best for Britain.
“My local Conservative Association in Clacton is thriving. It brims with those I’m honoured to call my friends.
“The problem is that many of those at the top of the Conservative Party are simply not on our side. They aren’t serious about the change that Britain so desperately needs.
“Of course they talk the talk before elections. They say what they feel they must say to get our support… but on so many issues – on modernising our politics, on the recall of MPs, on controlling our borders on less government, on bank reform, on cutting public debt, on an EU referendum – they never actually make it happen.”
On Mr Cameron’s pledge of an in/out EU referendum on 2017, after renegotiating powers back from Brussels, he said the prime minister’s advisers had “made it clear that they’re looking to cut a deal that gives them just enough to persuade enough voters to vote to stay in”.
He added: “Once I realised that, my position in the Conservative Party became untenable.”