Prime Minister Stephen Harper is defending the Conservative party's advertising spending in the 2006 federal election, saying it followed the rules.

But he told a news conference in New Orleans on Tuesday that if the official interpretation of the law changes, the Tories will adapt.

"This is the same story as before,"he said. "We always follow the law as it has been interpreted."

Harper, attending the North American leaders' summit, said the party disagreed with Elections Canada that some ad expenditures should have been charged to the national budget, not local ones.

Earlier, a Conservative MP claimed Elections Canada is showing bias towards his party in its handling of the election advertising controversy.

"We're very concerned with the conduct of Elections Canada," Pierre Poilievre told Canada AM.

But Deputy Liberal Leader Michael Ignatieff said the key issue is the Tories allegedly overspending on advertising in the 2006 federal election as well as its attacks on the agency.

"Pierre Poilievre and the party have been consistently attacking Elections Canada. You don't do that," he told Canada AM.

"These guys are resisting the institution that keeps our elections fair."

The controversy heated up with last week's search by the RCMP at Conservative party headquarters and Monday's release of the search warrant.

The Conservatives and Elections Canada are embroiled in a dispute over what's become popularly known as an "in and out" scheme. The party allegedly shifted money from its national office into 67 local ridings where candidates still had personal spending room. Those candidates then transferred the money back to the party to pay for ads. The ads that ran were largely identical to national ones.

The candidates were then able to claim reimbursement from Elections Canada. The total overspending is alleged to be $1.3 million.

"This whole legal dispute involves Conservative candidates spending Conservative funds on Conservative advertising," Poilievre said.

"Elections Canada wants the power to determine what constitutes a local advertisement and what constitutes a national one. But to do that, they have to dictate what local candidates are allowed to put in their advertising materials," he said.

"We think that in a free country, candidates decide what goes in their materials, and not a government bureaucrat."

Liberals tipped?

Poilievre noted a Liberal party camera "was suspiciously in tow" to document the April 15 raid.

Ignatieff scoffed at any suggestion Elections Canada had colluded with his party, saying the Liberals saw the search taking place on TV and sent someone down with a camera.

"We had no advance warning, to the best of my knowledge, that this was going to happen," he said.

"The deal here is whether (the Tories) spent within the election limits allowed by Elections Canada in a federal election," he said.

"They spent a million dollars more than they're entitled to in a national election," Ignatieff said, noting the limit is about $18 million.

"The cap's there for a very important reason -- so that every party fights on a level playing field," he said.

In this dispute, the Conservatives have "resisted and stiffed Elections Canada from the beginning," Ignatieff said.

Poilievre said other parties have done the same thing as his party, but Ignatieff said the fundamental issue is whether one stays within the spending cap.

The Globe and Mail, in an editorial published Tuesday, wrote that the Conservatives have "deployed a dizzying array of rhetorical devices" to deflect attention on the situation.

"They have attempted to link the raid to their lawsuit against one of those (Elections Canada) officials, even though there is no evidence of any connection," it said.

The paper also accused the Conservatives of making unfounded allegations against other parties.

"We have plenty of hard evidence," Poilievre said, adding other parties have admitted to engaging in much the same technique.

"We believe they're within their rights to do so," he said.