The Conservatives will adapt to any change in the official interpretation of elections spending laws, Prime Minister Stephen Harper said Tuesday, while insisting his party followed the law in the last federal election.

"Our position is that we always follow the law as we understand it," the prime minister said in response to a reporter's question at a joint news conference with U.S. President George W. Bush and Mexican President Felipe Calderon in New Orleans.

"We were following in the last election the interpretations that had been put on that law in the past," Harper said. "If those interpretations change, we will of course conform, but we will expect the same rules for every single party."

Elections Canada, with the assistance of the RCMP, raided Conservative party headquarters last week seeking documents about ad spending in the 2006 election, in which the Tories ousted Paul Martin's Liberals.

The Conservatives are accused of exceeding their campaign spending limit by more than $1 million, and making "false and misleading" statements in their financial returns, Elections Canada alleges in the warrant for the raid.

Harper said Elections Canada's position now is that some Tory ad expenditures should have been charged to the national budget, not local budgets.

"This is the same story as before," Harper said. "We have a different view."

Plan involved 67 candidates

According to the warrant documents, Elections Canada alleges the Conservatives overspent on election ads by disguising national ads as local expenses in an elaborate plan that involved the participation of 67 candidates, including four cabinet ministers.

The documents, about 700 pages that include search warrants and a sworn affidavit supporting the raid, allege the Conservatives engaged in a so-called "in-and-out" scheme — directing money to local candidates, who then transferred the funds back to the party to spend on more advertising for the national campaign.

The affidavit, signed by Elections Canada investigator Robert Lamothe, said this scheme allowed the party "to spend more than $1 million over and above" the legal campaign limit of $18.3 million set out under the Canada Elections Act.

None of the allegations has been proven in court.

But opposition parties said the matter is more than a debate over election spending rules. Liberal Leader Stéphane Dion said Monday the documents suggest the Tories "cheated" in the 2006 election campaign.

Sources allege 'campaign guru' Finley gave orders

Conservative sources speaking to CBC News were adamant that Harper was not told about the party's spending plans until long after the 2006 election.

But the Opposition Liberals said they are skeptical about statements that Harper didn't know about the plan.

"It's just not credible to argue that the prime minister didn't know about this," Liberal deputy leader Michael Ignatieff said Tuesday. "And their whole action has been consistent with his character, which is to win at any cost."

The Tory sources told CBC News the policy was put in place by the man some call their "campaign guru" — Doug Finley.

Finley was the campaign chair and is the party's political operations director and a key member of Harper's inner circle. He is married to Immigration Minister Diane Finley.

Finley was not targeted in the documents filed by Elections Canada to obtain the search warrant.

But two other Tory operatives were named — Michael Donison, former executive director of the party and current senior policy advisor to government House leader Peter Van Loan, and Patrick Muttart, now deputy chief of staff to the prime minister, who was in charge of advertising during the campaign.

The sources said both men took orders from Finley, who was also one of two senior party officials to meet with the late independent MP Chuck Cadman ahead of a critical confidence vote for the Martin government in May 2005.

With files from the Canadian Press