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Tom DeLay, once one of the most powerful and feared conservatives in the US Congress, confirmed today that he was resigning his seat in the House of Representatives after two criminal investigations that dealt a blow to his chances of re-election.

"I think I could have won this seat but it would have been nasty," Mr DeLay, the former House Majority Leader, said in an interview with Fox News. "It would have cost a fortune to do it."

First elected for a suburban district of Houston in 1984, Mr DeLay helped the Republicans gain control of Congress in the "Republican Revolution" 10 years later and was elected House Majority Leader in 2002.

Known for his fundraising prowess and a bare-knuckled political style which earned him the nickname "The Hammer", Mr Delay, 58, was a key conservative ally of his fellow Texan George W Bush.

But his fall from grace has been both sudden and brutal. He is under indictment in Texas as part of an investigation into the allegedly illegal use of funds for state legislative races.

Separately, his ties with the lobbyist Jack Abramoff caused him to formally surrender his post as Majority Leader in January soon after the lobbyist entered into a plea bargain as part of a congressional corruption probe.

President Bush said today that the Republican party would not suffer from Mr Delay’s decision to resign. "My own judgement is that our party will continue to succeed because we are the party of ideas," Mr Bush told reporters at the White House.

But Democrats said that his departure was a sign of wider problems facing the Republicans in Congress. "Tom DeLay’s announcement is just the beginning of the reckoning of the Republican culture of corruption that has gripped Washington for too long," said Karen Finney, a Democratic Party spokeswoman.

Mr DeLay called Mr Bush yesterday and the two men talked while the President was flying on Air Force One on his way back from Cincinnati, Scott McClellan, the White House press secretary, said. "The president thanked him for his service and all that he accomplished and wished him all the best," Mr McClellan said. "Congressman DeLay has been a good ally whom the president has worked very closely with."

Republicans said that they expected DeLay to resign within months although it is not yet clear whether Rick Perry, the Texas Governor, will call a special election to fill out the unexpired portion of his term, or whether the seat will remain vacant until it is filled in November.

DeLay relinquished the No 2 post in the House after his indictment in Texas last October, and decided in January against trying to get the post back. More recently, a former aide, Tony Rudy, admitted that he had conspired with Mr Abramoff and others to corrupt public officials, and he promised to help the broad federal investigation of bribery and lobbying fraud that already has resulted in three convictions.

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