A hand grenade has been thrown into David Cameron's general election campaign after the Eurosceptic Tory MP Douglas Carswell defected to Ukip, triggering an immediate byelection.
Carswell, a leading member of the generation of Tory Eurosceptics, said he had endured sleepless nights in the runup to his decision.
He has decided to resign immediately as MP for Clacton, in Essex, guaranteeing a difficult byelection for the Tories. As the sitting MP Carswell will have an immediate advantage.
Sitting alongside the Ukip leader Nigel Farage, Carswell said: "It's nice to be a member of a party where I agree with the leader." Farage joked: "It is early days."
Carswell said he believed David Cameron and senior Conservatives were not "serious about real change".
He had a majority of 12,068 at the last general election.
Among a list of criticisms, he insisted that the failure to take a stand against the European Union was at the heart of his decision.
"They are not serious about real change. It's above all the failure to deliver on the promise of political reform that has driven me to be here today," he said.
"Europe's the one continent on the globe that is not growing ... Yet who in Westminster, who among our so-called leaders is prepared to envisage real change?"
Carswell said: "Things don't have to be this way. I will be asking voters in Essex to help me change them."
He entered parliament in 2005, and has frequently rebelled over European issues.
Farage said the defection was "the bravest, noblest, most honourable thing I've seen in British politics in my life". In an interview with Sky News he claimed other Conservative MPs were "considering their options".
On Tuesday Farage was selected to fight the Conservative-held seat of South Thanet in Kent at next May's general election.
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