The director of the military's strategic joint staff was called to explain duelling figures on how much the Harper government spent on the NATO mission, which ousted dictator Moammar Gadhafi last year.
Maj.-Gen. Jon Vance defended Peter MacKay, the defence minister, who claimed last October the air and sea campaign was under budget and set back the federal treasury by only $50 million.
The actual incremental cost ended up being $103.6 million when all of the bills were tallied last February.
Vance says MacKay did not mislead the public and answered the question of how much had been spent up until that time.
But he concedes the minister would have known the estimated cost when he was questioned and did not speculate on why MacKay chose to go with the lower figures exclusively.
"He would have known what the estimated cost was — for sure," said Vance.
"The minister would have known what the all-up estimated cost of the mission could be. On that day, he knew what the cost of the mission was to that point in time."
Asked whether it would have been appropriate for the minister to disclose the estimate, Vance replied: "I don't do hindsight."
He also denied he was taking a bullet for MacKay, saying that it was the work of his staff that was being questioned.
Opposition parties slammed the Harper government for confusion and compared it to the figures fiasco surrounding the F-35 stealth fighter purchase, in which the auditor general accused National Defence of deliberately low-balling the multibillion-dollar estimate.
Vance told a hastily assembled news conference at National Defence headquarters that the total cost of the Libya campaign has not been hidden from Canadians, and pointed out senior military leaders referred to the figures publicly during Senate committee hearings.
The department has been "utterly transparent," said Vance, a former task force commander in Kandahar.
The incremental figure differs substantially from numbers presented this week in the parliamentary report on plans and priorities for National Defence.
It estimated the Libya mission, which saw Canadian CF-18s bombing targets and a frigate patrolling the North African coast, cost a total of $347 million.
But Vance says that figure, while accurate, reflects the total expense including the salaries of aircrew and sailors and other things that the military would pay for regardless of whether the campaign happened.
When it calculates whether to join an operation, the Defence Department looks at what it must spend over and above its normal budget — a practice that has constantly run afoul of the auditor general and has added fuel to the debate over the F-35.
In saying the military low-balled the stealth fighter purchase, auditor Michael Ferguson pointed to the exclusion of $10 billion in operating costs such as pay, fuel and other commodities that would be consumed in the life-time of the aircraft.
Opposition parties seized on the difference in the Libya figures.
"Is the government so incompetent that it still cannot get its numbers straight or was it misleading Canadians yet again?" asked Ontario New Democrat David Christopherson.
MacKay, Foreign Affairs Minister John Baird and even Prime Minister Stephen Harper were drawn Friday into the debate, which has tarnished the Conservative fiscal credentials.
Speaking after question period, Baird did not step up to defend MacKay and directed reporters to the defence minister to answer why he chose to go with the lower figure in public last fall.
The prime minister played down the conflicting estimates.
"I think it's important to note that the number you cite includes — most of that number are frankly ongoing, normal operations of the Canadian military," Harper said during an event in Edmundston, N.B.
"We always give the most up-to-date figures and it's important also to note, as I say, not only that these figures include normal operations of the Canadian military of those assets over that period, but that all of these numbers, all of the costs of the Libya mission were accomplished within the budgets set by the government for the Department of National Defence. So this is not new money."
Neither the Liberals nor the NDP were buying the explanation and accused the government of lying about the cost of foreign military adventures.
Baird chose to focus his remarks in praise of the military, but stumbled at one point when referring to the air force's bombing campaign in support of rebel forces in Libya.
"They saved literally thousands and thousands of innocent civilians and Liberals, uh, innocent civilians and Libyans," he said to laughter from both sides of the Commons.
"The Canadian Forces are remarkable, but not that remarkable."
— With files from Tara Brautigam in Halifax