OTTAWA - Prime Minister Stephen Harper has testified that he personally authorized an offer made to late MP Chuck Cadman in 2005 in exchange for his help defeating the Liberal government.

But he maintained he knew nothing about an alleged offer of a $1 million life insurance policy to get Cadman's vote, saying he only approved an offer of campaign financial support in the event of an election.

In sworn testimony filed Wednesday in Ontario Superior Court, Harper said he authorized his campaign manager, Doug Finley, to approach Cadman after Finley told him he had heard Cadman was willing to side with the Tories but couldn't because of financial distress and fear of losing an election.

The testimony given two weeks ago was Harper's first detailed account of his role in the so-called Cadman affair. During four hours of testimony, he offered two different versions of when he learned about Cadman's financial troubles.

Harper said he approved the overture to Cadman on May 18, 2005, the day before a crucial confidence vote, after receiving a message through one of his assistants from Finley.

The prime minister has launched a $3.5-million libel suit against the Liberal party. His testimony was part of a cross-examination by a lawyer working for the Liberal party. Harper's testimony was given under oath in Ottawa in the boardroom of the law firm that is representing him. Officers of the court as well as lawyers for all sides were present.

He testified that he gave permission for Finley to speak to Cadman, a former Conservative, even though he was sure Cadman was going to support the Liberals in the confidence vote.

This is Harper's only lengthy explanation of his actions in the Cadman affair. Cadman's family has asserted that the Conservatives offered Cadman a $1-million insurance policy to help defeat the Liberals. Harper has said he knew nothing of an insurance policy and sued the Liberals for defamation when they posted an article on their website suggesting otherwise.

The prime minister has also sought a court order to prevent the Liberal party from using or distributing copies of an audio tape at the centre of the libel suit.

The tape contains an interview a British Columbia author conducted with Harper in 2005 about attempts Conservative party operatives made to convince Cadman to help defeat the minority Liberal government in the Commons.

Harper is heard telling author Tom Zytaruk in 2005 that he was aware Conservatives had discussed "financial considerations" with Cadman as they tried to coax him into opposing the Liberals during a confidence vote.

Harper testified that he personally met Cadman on April 1 that year in an attempt to coax him back to the Conservative fold, after having authorized a similar approach by former Tory MP John Reynolds as early as the previous fall.

Under cross-examination by the Liberal party lawyer, Harper initially said Finley informed him about Cadman's worries over finances and life insurance the following September.

Cadman had terminal cancer at the time of the 2005 confidence vote which the Liberals survived thanks to Cadman's support and died later that summer. Harper is suing the Liberals over suggestions posted on their web site that he was aware of a bribery attempt in the affair.

But Harper testified during the examination that the only offer to Cadman he authorized was the one requested by Finley the day before the May 19 confidence vote.

He said he first learned of the insurance policy, as well as Cadman's financial straits, when Dona Cadman told him of the offer during a personal visit he made to her house on Sept. 9, 2005, where, after his talk with Dona Cadman, he was interviewed by Zytaruk.

"When I talked to Doug subsequent to my conversation with Dona and Tom Zytaruk, and I started to inquire, we started to bang heads together about where this story was coming from," Harper said.

"Doug told me, you know, he didn't source it, but he told me that he had heard stories about Chuck being concerned about his finances and being concerned about insurance, but he said, in fact, Chuck had never raised any such matter with him," Harper said.

"My first reaction to the story was it sounded preposterous to me. I couldn't understand how or why anyone would offer a man with cancer a life insurance policy . . . and Doug Finley certainly wouldn't have done it because Doug is not a . . . personal benefits man".

But as Liberal lawyer Chris Paliare pressed Harper about whether he had been told by anyone earlier that Cadman was worried about financial security, the prime minister offered new details.

"Maybe I should add to you where this came up firstly," he said. "This is when Doug Finley called me through my executive, Ray Novak, on the 18th, and he asked permission to approach Chuck Cadman on behalf of the party to get him to rejoin the caucus, and that the story was that Chuck wanted to vote with us in Parliament as he usually did, and that he would want to rejoin the caucus and fight with us in an election campaign, but that he couldn't because he didn't have, you know, he didn't have the financing, he would have lost the election, et cetera, et cetera".

Harper testified that his initial response was that he believed Cadman was going to vote with the Liberals, based on his earlier April 1 discussion with Cadman.

The prime minister said party members were conveying the message "aggressively" to him that then-prime minister Paul Martin and other Liberals had approached Cadman seeking support in the Commons vote and that he "had a responsibility to make sure that Chuck was formally approached and that it was clearly understood that he could rejoin the caucus, that he could get the nomination, there was no doubt about that, and that he would be a priority for the party in terms of re-election and financial support. And on that basis, I authorized the meeting on the 19th."

Though Harper has not taken any legal action against Zytaruk, he has contended since last June the tape of the interview Zytaruk conducted with him outside Dona Cadman's home was doctored.

He has since said the financial considerations included campaign expenses and support, but added more detail about Finley's offer during the cross examination.

"(Finley) said he had no offer of a policy of insurance, he was there to lay down for Chuck that he could join the caucus, that he would automatically get the nomination, and the party would take care of squaring that away in the riding, that he would become, this is the detail that Doug gave me at the time, that he would become part of what we call the target seed voter program which has a number of various benefits for candidacy that is high priority for the party in terms of financial support, in terms of services and other kinds of campaign support".

Under further questioning, Harper said the assistance would have included a repayable loan to Cadman's riding association not to the candidate personally.

The Liberals' lawyer pressed Harper about whether the insurance policy Dona Cadman described may actually have been a top-up to Cadman's life insurance as an MP should he lose his seat in an election. Harper said he was unaware of those kinds of details.

Paliare also probed Harper over the difference between offers of financial assistance or aid to reimburse candidate expenses and offers made "for securing a vote to bring down a government."

Harper rejected the comparison, saying his party "cannot agree under any circumstances to provide a personal benefit" to a candidate before or after an election. He said the party can only agree to transfer money in accordance with electoral law to its own candidate".

Paliare also questioned Harper over the prime minister's claim the Zytaruk tape had been doctored and Harper said several times during the examination that he believed Zytaruk himself altered the tape.

A Superior Court hearing is scheduled for Sept. 22, likely in the midst of a federal election campaign, where expert evidence on the authenticity and integrity of the tape will be heard.