Prime Minister Stephen Harper has dropped a libel suit against three Liberal MPs but is proceeding with one against the Liberal Party of Canada, making it the first time a sitting prime minister has sued the opposition for libel.

The defamation suit concerns bribery allegations published on the Liberal Party's website concerning the Chuck Cadman affair.

The suit is claiming up to $2.5 million in damages for Harper.

A court document obtained by The Canadian Press reveals Harper's lawyers are seeking $1 million in general damages, $1 million in aggravated damages and $500,000 in punitive damages, along with legal costs.

Harper has hired a high profile libel lawyer to represent him, CTV's Ottawa Bureau Chief Robert Fife reported Thursday.

Last week, Harper filed notice of libel against Liberal Leader Stephane Dion, deputy leader Michael Ignatieff and Liberal Party house leader Ralph Goodale over allegations that he was aware that a $1-million insurance policy had allegedly been offered to independent MP Chuck Cadman in 2005 in exchange for his support on the eve of a historic confidence vote.

But the three MPs have been dropped from the libel suit. The suit now names only the Liberal Party, the Federal Liberal Agency of Canada and the unknown authors of the report on the Liberal website.

The suit certainly didn't have a dampening effect in the House of Commons as Harper took heated questions on the Cadman affair from both Dion and Bloc Quebecois leader Gilles Duceppe during question period Thursday.

Dion accused Harper of avoiding questions on the subject and said that the public is also asking questions of the prime minister.

"(Harper) won't be able to threaten (the public) with a lawsuit," Dion said.

Dion also said he's "very confident'' his party has done nothing wrong.

"We will not apologize. Come on. We want the truth from the prime minister,'' he said.

Regarding the lawsuit, Harper said he did what any Canadian would do if they felt their reputation was at stake.

"I look forward to seeing the leader of the opposition actually let this go to trial so he can hear the whole truth and admit his own role in it," Harper.

Harper has categorically denied having any knowledge of any offers being made, but feels he has been libelled by statements published on the Liberal website.

Who will pay?

A Liberal official said earlier this month the party might ask the Commons to pay the three Liberals' court costs.

It's unclear whether the Liberal Party has the money to fight the court battle, as it might not qualify for the Commons to cover its legal fees.

Meanwhile, the Conservative party is covering Harper's legal costs. Any financial award would go to the party's legal bills, said the prime minister's communications director, Sandra Buckler.

The rest would go to a yet-undecided charity.

A tape that emerged last month is at the centre of the controversy.

Harper appears to suggest in the tape that he knew "financial considerations" were offered to Cadman.

The court document claims the tape was doctored but Cadman biographer Tom Zytaruk, who recorded the interview with Harper, disputes those claims.

The filing says Harper's close confidants Doug Finley and Tom Flanagan met with Cadman for 15 minutes on May 19, 2005.

It says the three men discussed how Cadman "could become the Conservative party candidate in Surrey North in the next election under the then-current rules of the party and what campaign support the party could provide for his re-election."

In Zytaruk's book, Cadman's widow says two Tory operatives offered the dying MP a $1-million life insurance policy in exchange for his support in the May 2005 vote, which could have toppled Paul Martin's Liberal minority government.

Two other family members have backed up her story.

But Conservative party spokesman Ryan Sparrow has told CP that Finley and Flanagan offered a repayable loan to Cadman's local riding association to cover campaign expenses if he rejoined his former party.

The court document says the terminally-ill Cadman, who died of cancer in July 2005, wanted to run in the next election.

With files from The Canadian Press