The federal Liberals want a jury to decide if they are guilty of libelling Prime Minister Stephen Harper over the so-called Cadman Affair and whether his $2.5 million lawsuit against the party should be rejected.

In a statement of defence filed in the Ontario Superior Court of Justice on Tuesday, the Liberal Party of Canada says Harper's claim should be dismissed, arguing his legal action is a "fundamental attack on the freedom of political expression."

They also ask that "this action be tried by a jury."

Harper's suit stems from statements published on the Liberal party's website alleging the Tories offered a bribe to the late Independent MP Chuck Cadman to secure his co-operation on a crucial budget vote that threatened to topple the Liberal minority government in May 2005.

Harper's lawsuit cites a Feb. 29 article published on the Liberal Party's website entitled, "Harper knew of Conservative Bribery" and a Feb. 28 story that ran with the headline, "Harper must come clean about allegations of Conservative bribery, Liberals say."

In their statement of claim, the Liberals defend the articles, saying they were published without malice, are of public interest and that criticism of the government is protected under the Charter.

"The reports were published in good faith and in accordance with the Defendants' legal, moral, social and profession duties to engage legitimate public debate," the statement of claim says.

According to the statement of claim, the Liberals "expressly" deny that the words are defamatory of Harper, but if they are, then they are "true or substantially true."

As well, the Liberals deny Harper has suffered damage to his reputation and reject the damages he's seeking as "excessive, exaggerated, remote."

But they add that if Harper's reputation was damaged, then he brought it upon himself for refusing to answer questions about the controversy.

Speaking about the lawsuit in the House of Commons last March, Harper said " the Liberal party and its agents have been making allegations against me that are of a criminal nature, that are absolutely false and that are despicable."

"I have every right, as does my family, to defend our reputation, and Mr. Speaker, the Liberal party will come to regret engaging in this illegal and untruthful behaviour," he said then.