European parliament vice-president Edward McMillan-Scott has joined the Liberal Democrats after being thrown out of the Conservative party.
Mr McMillan-Scott had the Tory whip withdrawn after he stood against the Conservative-approved candidate for the European parliament vice-presidency, Michel Kaminski.
He had opposed the Tories' decision to leave the main centre-right grouping in the European parliament, the European People's party, in favour of the smaller European Conservatives and Reformists group.
Having spent several months as an independent MEP Mr McMillan-Scott has now joined the Lib Dems.
The transition has been eased by the fact, he explained, that "most of my family are liberals".
"I have been around the higher circles of the Conservative party for long enough to fear that, on Europe, Cameron says one thing in opposition and will do another in government," he said.
"From being a liberal Conservative I become a conservative Liberal."
Lib Dem leader Nick Clegg praised Mr McMillan-Scott's record fighting for human rights and democracy around the world.
"As someone of principle he has refused to cosy up to right-wing extremists, despite pressure from the Tory machine," he said.
"This flies in the face of David Cameron's claims of change. It shows that people of principle, who believe in fairness and want real change for Britain are at home in the Liberal Democrats."