Two former Conservative peers are expected to defect to the UK Independence Party (Ukip) today, giving the group its first foothold in parliament.
Lord Pearson of Rannoch and Lord Willoughby de Broke were Tory peers but had the whip withdrawn in 2004 for helping Ukip, and have been sitting as independents. They now hope to persuade others to defect to a new Ukip grouping in the House of Lords.
Party leader Nigel Farage welcome the move as an "important step" in Ukip's development - although the party did well in the 2004 European elections, and has ten MEPs, it has failed to translate that success into parliament.
"To have a foothold in Westminster will make quite a difference. It means we have a voice inside the Westminster village, which has been badly needed. It will also help us raise money," he said.
The defections are a major blow to David Cameron, the Conservative leader who has been forcing his party towards the political centre ground for the past year, to the outrage of many more traditional members.
Lord Pearson, chairman of PWS insurance broker, told The Times that he was turning to Ukip because he had given up hope of a Eurosceptic Tory party.
Mr Cameron made noises in that direction early in his leadership, with the pledge to change the Tories' grouping in the European parliament, but has since backed off. He has dismissed Ukip as a party full of "fruitcakes and loonies and closet racists, really".
Lord Pearson said: "We've really given up hope that under its present leadership the Conservative party will be appropriately Eurosceptic by the next election. Under David Cameron, the leadership has become a lot more Europhile even than it was under Michael Howard."
Lord Willoughby de Broke added: "This country's best interests are served outside the European Union, and Ukip is the only party campaigning for that. Some will say we have let the Conservative party down, but the party has let us down, and the country down."
Reports suggest Ukip finally managed to woo the two peers after pledging to abandon its policy of fielding candidates against the Tories, even when the latters' candidates were proven Eurosceptics. This should improve the party's standing among Conservatives.
The defections are only the latest to hit Mr Cameron - last month, the former chairman of William Hague's constituency, Toby Horton, and approved Tory candidate Mark Hudson, left the Conservatives to join Ukip.
However, the Eurosceptic party has been hit by troubles - last night its Plymouth branch closed down after the chairman and 11 others resigned to start a new grouping.