Conservative MP for Rochester & Strood Mark Reckless has quit the party for rivals Ukip, he has announced at Ukip's party conference in Doncaster to a loud ovation. Reckless is the second Conservative to join Ukip, following MP for Clacton Douglas Carswell in August.
Reckless said his decision had been a difficult one. "These decisions are never easy, but it is a decision I make from optimism, a decision that is born from the belief that Britain can be better."
The economist and lawyer said he was joining Ukip as it would be impossible to honour his promises to voters as a Conservative.
"I remember the promises I made to my constituents in Rochester and Strood at the last election, and I intend to keep them. I found that it's impossible to keep these promises as Conservative and that is why I am joining Ukip."
A spokesperson for Conservative Party said: "Mark Reckless' decision to join Ukip is completely illogical. He says he wants action on a European referendum, tax and immigration. The only party capable of delivering on these issues is the Conservative Party – and a vote for Ukip is a vote for Ed Miliband."
Reckless has a reputation for being the most rebellious of all Conservatives MPs. He is credited with strategising the coalition's first defeat - a real-terms cut in the EU budget - and voting against the rise in university tution fees.
It is not yet known whether Reckless, elected as MP in 2010 with a majority of 9,953, will contest the seat for the anti-Europe party led by Nigel Farage.
In 2010 Reckless admitted being too drunk to vote on a key budget vote. According to the Daily Mail, he fell over in a Commons bar and had to be bundled home.