OTTAWA - Prime Minister Stephen Harper has upped the ante in his $2.5 million defamation suit against the Liberals, claiming an additional $1 million for "misappropriation of personality."

The potential blow to the Liberals' already depleted coffers came to light Wednesday as part of the 2007 annual financial statements filed by all federal political parties with Elections Canada.

The statements underscore just how little the Grits can afford to lose such a costly lawsuit: Harper's Conservatives vacuumed up donations last year at almost four times the rate of the cash-strapped Liberals, drawing on a pool of donors almost five times larger.

Harper launched his $2.5-million lawsuit against the Liberal party last March, after Grit officials refused to apologize for accusations that the prime minister knew about a "Conservative bribery" attempt in the Cadman affair.

The accusations, posted on the Liberal website, stemmed from a book on the late independent MP Chuck Cadman. Author Tom Zytaruk alleged that two Conservative officials offered Cadman, who was dying of cancer, a $1-million life insurance policy if he agreed to vote with the Tories in a crucial 2005 confidence vote.

Sources say Conservative and Liberal officials met in the spring to discuss a possible out-of-court settlement. But negotiations broke down and shortly thereafter, on June 4, Harper added another $1-million claim to the suit.

According to the Liberal financial return, Harper is claiming the additional damages for "misappropriation of personality and injunctive relief." The Liberal party "intends to fully defend this claim."

Conservative party spokesman Ryan Sparrow confirmed the additional claim but declined further comment.

The Tories have also gone to court seeking an injunction to prevent the Liberals from using what they claim is a "doctored" audio tape, recorded by Zytaruk. On it, Harper appears to acknowledge knowing about "an offer" made to Cadman "to replace financial considerations he might lose due to an election."

Harper has called the Liberals' bribery accusations "despicable" and has predicted the party will "come to regret engaging in this illegal and untruthful behaviour."

The Liberals can ill-afford to lose in court. According to the 2007 financial returns, the party raised just less than $4.5 million last year from 23,442 donors -- miles behind the Tories and just marginally ahead of the NDP, traditionally the poor cousin of the three main national parties.

The Conservatives were awash in cash, raking in almost $17 million from 107,492 donors.

The NDP pulled in almost $4 million from 23,303 contributors and the Bloc Quebecois, which runs only in Quebec, raised $429,971 from 4,486 donors.

The detailed returns show the Tories are an incredibly efficient fundraising machine adept at the art of getting regular, small amounts from thousands of donors. The party spent only $41,000 on fundraising in 2007, meaning it spent less than a penny for every dollar it raised.

"We're a big, member-driven party," said Sparrow.

"People respond to strong leadership and clear ideas."

All that cash enabled the Conservatives to spend $4.2 million on advertising last year -- almost all of it on televised ads attacking Liberal Leader Stephane Dion.

By contrast, the Liberals spent over $600,000 on fundraising -- about 13 cents for every dollar they raised-and could afford to spend only $543,000 on advertising.

Liberal spokesman Daniel Lauzon acknowledged that 2007 was a "challenging year" for the party. It is still struggling to adapt to the ban on corporate donations and restrictions on individual contributions, imposed in 2004 and tightened further by the Tories in 2007.

But Lauzon said Liberals are making the "transition" and starting to show results. As proof, he pointed out that Liberal donations during the first quarter of 2008 were 60 per cent higher than the same period last year, although the Tories still managed to rake in five times more.