OTTAWA–The troubled Toronto Port Authority is again turning to the federal auditor general in a bid to silence critics amid a controversy over finances involving Natural Resources Minister Lisa Raitt

Auditor General Sheila Fraser advised the independent, federally funded authority in September that she has no mandate to audit the organization. But Mark McQueen, chairman of the authority's board of directors, wrote Fraser again Wednesday pleading with her to change her mind.

In his letter, McQueen says Fraser's refusal to get involved "was unfortunate news."

He is trying to refute allegations raised in a Toronto Star series on the port authority of irregularities in the payment of questionable expenses involving Raitt.

McQueen points out that the authority has received a clean bill of financial health for its 2008 financial statements from its independent auditor, Deloitte LLP.

That hasn't stopped opposition parties from raising the matter in the Commons, zeroing in on the fact that Raitt, who used to be president of the port authority, has been accused of signing off on at least one of her own expense claims.

"As the TPA has nothing to hide and has done its best to be as open and transparent as possible, your inability to review these accusations has given TPA detractors the luxury of claiming that there remain unanswered questions regarding the financial, operating and governing affairs of the TPA," McQueen wrote to Fraser.

McQueen argues it's in the public interest for Fraser to provide "a second independent, objective, fact-based review that all stakeholders may rely upon."

Barring that, McQueen asks Fraser to at least agree to review a special audit the authority is prepared to have conducted by "an independent, arms-length third-party accounting firm," other than Deloitte.

Raitt has cast herself as someone unjustly caught in the middle of a dispute between feuding factions on the authority's board.

Among other things, former board chair Michele McCarthy has alleged to the Star that she refused to approve a $3,000 expense claim for a trip to London, England, so Raitt signed off on it herself.

The authority says that claim and other allegedly questionable expenses were pre-approved in its 2008 budget process.

Raitt has also come under fire for a political fundraiser that was organized out of the port authority's offices, using its email address list.

The Liberals have asked Elections Canada and Parliament's independent ethics and lobbying watchdogs to investigate that affair.