Michael Ferguson made a repeat appearance Tuesday before the Commons public accounts committee, saying he stands behind the facts and figures in his April 3 audit, which set off a heated political debate.
"I am concerned with suggestions that accurate estimation and the inclusion of personnel, operating and maintenance costs are not important, since they would be incurred regardless of the aircraft selected to replace the CF-18," the auditor told the all-party committee.
His report accuses National Defence of hiding the full cost of the F-35 program by not publicly reporting $10 billion in operational expenses and criticizes Public Works for not demanding more justification for the sole-source purchase.
Ferguson went on to say that cabinet was aware the program would cost over $25 billion when it approved the stealth fighter program in principle in 2008.
In an appearance before the same committee a couple of weeks ago, deputy defence minister Robert Fonberg dismissed the comments by saying the auditor "got it wrong."
He said it is not the practice of National Defence to include all life-cycle costs in project estimates, but the auditor pointed out it is required by the department's own policies and the federal Treasury Board, which sets the standard across government.
Defence Minister Peter MacKay has called the discrepancy an accounting difference.
The auditor general's method of calculating costs, including the service life of the aircraft and operational expenses, has been questioned.
New Democrat procurement critic Matthew Kellway said the government should stop attacking the auditor general.
But Associate Defence Minister Julian Fantino denied the Conservatives were challenging Ferguson.
"We have, as was indicated, accepted the findings. We are acting on the recommendation of the Auditor General," he told the Commons on Tuesday.
Within hours of the report being made public on April 3, the Harper government announced it was taking the procurement away from National Defence and giving it to a secretariat under the umbrella of Public Works.
It established a seven-step process and promised to re-examine the entire troubled fighter program, which has been beset with development delays and massive cost overruns in the U.S.
Despite that officials, including Fonberg and the chief of the air staff say the F-35 remains the only option the government is considering.
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