Prime Minister Stephen Harper said Thursday there is "absolutely no truth" in allegations that Conservatives tried to bribe a dying Independent MP in 2005, although a recording of an interview he gave at the time seems to suggest otherwise.

In a raucous session of question period on Parliament Hill Thursday, Harper told the House that he investigated claims the Conservatives offered a million-dollar life insurance policy to the late Chuck Cadman just two days before a critical vote on May 19, 2005.

"There is absolutely no truth in it," the PM said.

The allegations were made by Cadman's wife, Dona, in a forthcoming book, Like A Rock: The Chuck Cadman Story.

Cadman, a B.C. MP who was battling cancer and died in July 2005, ultimately sided with the ruling minority Liberals in the vote, ensuring Canadians would not head to the polls for a summer election. The Conservatives were the official Opposition at the time, and Harper was at the helm of the party.

Harper is quoted in the book, and appears to confirm that some sort of financial arrangement was offered to Cadman. He was interviewed by the book's author, Vancouver journalist Tom Zytaruk, shortly after Cadman's death in 2005.

CBC News has obtained a copy of the audio recording of the interview.

"The insurance policy for a million dollars, do you know anything about that?" Zytaruk asks.

"I don't know the details. I know that there were discussions," Harper replies on the tape. "This is not for publication?"

"This will be for the book, not for the newspaper," answers Zytaruk, who works for a Surrey newspaper.

Harper goes on to explain on the tape that the offer to Cadman was "only to replace financial considerations he might lose due to an election." He adds that the offer was carried out by people who were "legitimately representing the party."

He also tells Zytaruk that he knew there was little chance Cadman would agree.

"They wanted to do it, but I told them they were wasting their time. I said Chuck had made up his mind," Harper said.

Federal Liberals have asked the RCMP to investigate the allegations. They sent a letter to the Mounties on Thursday, noting that under the Criminal Code of Canada, it's illegal for anyone to try to influence a member of Parliament by offering financial incentives.

"That's why we believe the RCMP need to look into this," Liberal justice critic Dominic LeBlanc told CBC News.

Earlier during question period, Liberal Leader Stéphane Dion decried the alleged offer to Cadman as "morally and ethically wrong," as well as illegal.

"Now we learn that the Conservative party tried to bribe him and the prime minister was aware of it, but Mr. Cadman could not be bought," Dion said. "What was the prime minister thinking?"

Harper pointed out that Cadman himself said in a national television interview that there had been no offer to win his support.

"I wish everyone would accept his word," Harper said.

The prime minister also praised Cadman, a former Reform and then Canadian Alliance MP, as a "fine man" and said Dion should apologize for questioning the late MP's credibility.

"I knew Chuck Cadman very well," Harper said. "The leader of the Opposition would have us believe that Chuck Cadman was offered a bribe, then went on national television and denied it ever happened. This is completely false, completely irresponsible and the leader of the Opposition should offer an apology."

Liberal Deputy Leader Michael Ignatieff later shot back: "Is he saying that the widow of Chuck Cadman is lying?"

Cadman's wife, who is now the Conservative candidate for Surrey North, was sticking by her story Thursday.

She is quoted in the book as saying: "That was on him, so that if he died, I'd get the million dollars." She adds that her husband was offended by the offers.

In an interview with CBC News Thursday, Cadman's daughter, Jodi, corroborated her mother's story, saying her father discussed the offer with her and her mother because he couldn't talk about it publicly.

"He just said 'I have something to tell you,' and he told me that he was offered a life insurance policy, that my mom and myself would be taken care of," she told CBC News in Vancouver on Thursday.

"When he told me, actually I have to admit I burst into tears because the position he was put in," she added, noting it was hard for him to turn down something that would have benefited his family.

New Democrat MP Pat Martin has put a motion before the federal ethics committee calling for an investigation of the allegations. He said he was "furious" about the allegation and that the matter should bump everything else off the list.

The committee now plans to examine the Cadman issue on Tuesday.

The chair of the committee, Liberal MP Paul Szabo, said he supports an investigation but cautioned against casting judgment, saying the statements are just allegations.

"It's certainly something I would favour because to the extent that this matter would linger out there with swirling allegations and all kinds of hearsay. The quicker that this matter be addressed in an appropriate forum, the quicker that you can resolve the real issues and hopefully ensure that no person is unduly harmed by the allegations, which may prove to be unfounded," he told CBC News.

"I certainly just want to caution everyone who's at all involved with this to be very, very careful. People's reputations and careers may be affected here, and we have to show dignity and respect to all people who may or may not be involved."

Szabo said that if a sitting MP is found to be directly or indirectly involved in trying to influence another MP's activities, they could lose their seat and be prohibited from running in a future election for five years.

Szabo said while it's possible that Harper could appear before the ethics committee, they would want to focus on the principals alleged to have been involved.

In his book, Vancouver journalist Tom Zytaruk writes that Chuck Cadman was visited by two Conservative party representatives in his office two days before the crucial vote and presented with a list of enticements to side with their party, including an offer of a million-dollar life insurance policy.

The two representatives are not named in the book, which CBC News has obtained a copy of. It will be published next month.

Zytaruk said he stands by the information in his book.

"I've got Dona saying that this happened and the executive assistant who was in the office with him at the time doesn't really want to speak about it but says that Dona has no reason to fabricate anything, and Stephen Harper speaking his piece," he told CBC News.

Zytaruk said he has been told the offers were made to Cadman on May 17, 2005, two days before the vote.

In a statement issued Thursday, Doug Finley and Tom Flanagan said they met with Cadman on the day of the vote to talk about his possible move to the Conservative fold.

"We offered ways that we — as campaign officials — could help Mr. Cadman in the Conservative nomination process, and if successful, wage a competitive campaign in a general election," the statement said.

Cadman, they said, confirmed later that evening that their "offer of campaign assistance" was the only offer presented.

Dan Wallace, Cadman's legislative assistant who is also quoted in the book, said in a statement Thursday that he was not at the meeting with the two Conservative party representatives, and therefore was not privy to the details.

The Liberals say there are too many questions that need answers, such as the discrepancy between the May 17, 2005, meeting described in the book and the one two days later described by the Conservatives.

There is also the question of how anyone could offer an insurance policy to a terminally ill man.

John Reynolds, a former Conservative MP from B.C., said the story seems fishy.

"Sounds to me like some kind of fiction story," he said. "How do you get a million-dollar policy for a guy who's dying? I mean, who's going to write that policy?"

He said he was a long-time friend of Cadman's, and Cadman never mentioned the insurance offer.