WASHINGTON — Former House Majority Leader Tom DeLay, R-Texas, was both defiant and ebullient Monday after hearing that the Justice Department had dropped its six-year investigation of his interactions with lobbyist Jack Abramoff and a host of other political contributors for whom he allegedly did political favors.

“I always knew this day would come,” DeLay, 63, said from his Sugar Land, Texas, home. He said he has no regrets about his conduct in Washington, insisted his actions were always legal, and assailed what he called the “criminalization of politics” by a federal ethics enforcement process he considers deeply flawed.

His celebratory remarks came a week before he is slated to return to a Texas courtroom for a pretrial hearing on allegations of felony conspiracy and money laundering, which still could put DeLay behind bars. His 2005 indictment in that Texas case is what short-circuited his three-year tenure in one of Washington’s most powerful jobs.

The Justice Department declined comment about DeLay’s claim of exoneration, following its policy of not discussing the status or termination of its criminal investigations. A source familiar with the inquiry confirmed that it had ended.

Speaking on the condition of anonymity, he said the main reason for dropping the effort was that prosecutors were unable to compel incriminating testimony by a former DeLay aide, Edwin A. Buckham, and find other witnesses or evidence that could have led to a conviction.

Buckham has similarly been cleared by the Justice Department, a source close to DeLay said. Buckham’s attorney, David Geneson, declined to comment.

The Justice Department investigation focused in part on payments made by Buckham, a former adviser who was a registered lobbyist in 2000, to cover some of DeLay’s expenses on an overseas golf trip.

Doing so violated House rules, but DeLay said he was unaware of the payments. Buckham’s now-shuttered firm employed DeLay’s wife, Christine, from 1998 to 2002 and set up a retirement account for her. A political action committee that Buckham controlled employed both DeLay’s wife and his daughter.

The payments amounted to nearly $500,000, drawn partly from revenue from corporations and their officers that had interests in legislation pending before the House.