Ian Brodie, Harper's departing chief of staff, told the Commons operations committee that there was no attempt in the Prime Minister's Office to derail the campaign of Senator Barack Obama over NAFTA.

The leaked document, a report of a meeting between Canadian diplomats in Chicago and a senior Obama campaign official, suggested there was more politics than substance in the senator's campaign trail attacks on the free-trade agreement.

Harper "remains furious about that to this day," said Brodie.

There were allegations in the Commons that Brodie was the source of the leak.

"These allegations were and remain completely false," he told the committee.

Brodie's testimony before a room of skeptical opposition MPs came a day before Senator John McCain, the Republican presidential candidate, was to speak in Ottawa on trade issues.

New Democrats suspect the leak was a deliberate attempt to hurt Obama's political prospects, but Brodie flatly denied any effort to help or hinder any American campaign.

Brodie, who is leaving the chief of staff job after 2 1/2 years, denied leaking confidential information about the Chicago meeting. A report issued last month after a two-month investigation of the scandal exonerated Brodie and Michael Wilson, Canada's ambassador in Washington, but couldn't finger the source of the leak.

Although Brodie is stepping down, he denied that his departure was linked to the scandal, saying he'd had enough of the 24-hour-a-day, 365-days-a-year job.

Two investigators from a heavyweight private security firm hired by the Privy Council Office to pursue the leak told the MPs they felt they were given full authority and co-operation in their work.

They interviewed bureaucrats, diplomats and others, traced computer e-mail files and inspected phone and fax logs in their fruitless search for the culprit.

They laid some blame on Foreign Affairs for failing to treat the document as secret or even confidential - it was actually left unclassified - and for distributing it far and wide.

They concluded that someone faxed the document to The Associated Press in the U.S.

As for Brodie, they decided that he hadn't passed on classified material to a journalist during a chat in the lockup for the federal budget. In fact, they said, speculation about Obama's stand on NAFTA was a subject of wide debate in Washington.

"That was being talked about in the capital," said Patrick Cummins of BMCI Investigations and Security.

Although Brodie had visited Washington the day before the budget, "there was no briefing on NAFTA for the chief of staff by anyone at the embassy."

Brodie didn't see the actual diplomatic memo until after the story first broke.

The uproar began at a time when the U.S. Democratic party primaries were being fought out in troubled manufacturing states, with the two candidates blaming NAFTA for vanished factory jobs.

During the media lockup for the Feb. 26 federal budget, Brodie made a candid comment to reporters suggesting that Senator Hillary Clinton's campaign had told the Canadian embassy not to worry about her anti-NAFTA comments on the campaign trail.

CTV reported that, along with a claim that Senator Obama's campaign had delivered the same message.

Wilson denied that he himself had spoken to Clinton's campaign, but said the embassy had been in contact with all the presidential campaigns.

The stories ignited a political row in the U.S. and some blamed the furor for Obama's loss in the Ohio primary in March. The suggestion was that Obama talked tough on the hustings, while privately reassuring Canada that NAFTA was safe.

Then the AP obtained the leaked report, originating from the Canadian Consulate in Chicago and detailing a meeting between an Obama adviser and Georges Rioux, Canada's consul general.

The Chicago report said the adviser told Rioux that Obama's attacks on free trade were more politics than policy.