Of the total, $406 million is expected to be spent in the new budget year that began Wednesday, on top of the projected $122.5 million that was set aside in the fiscal year that just ended.
Those are the incremental costs — the amount of money the Department of National Defence spends over and above the routine expense of maintaining an army.
The federal Treasury Board's plans and priorities report for the coming fiscal year, released Tuesday, showed the price tags for overseas operations in both the Middle East and eastern Europe were classified.
Both opposition parties complained, calling the decision to hide the dollar figures unacceptable, but Kenney said the information simply wasn't available when the estimates were completed in early March.
The $528.5-million estimate is likely not the last word on the question of costs, because there will be tear-down expenses should the next federal government decide to end the combat mission next March.
"I offer a caveat. That number will obviously change," Kenney said on the way into question period.
"If the past is any guide, it'll change upward, but that's our best estimate. And it's on that basis that cabinet approved additional funding."
Last month, the parliamentary budget office estimated in a February report that one year of combat operations would cost between $242 million and $351 million.
Both Kenney and Prime Minister Stephen Harper suggested there was no attempt to hide the figure, claiming it was released last week. A spokeswoman in Kenney's office said the numbers were revealed during a conference call with ethnic media, which took place around the time the Commons was debating the motion to extend and expand the deployment.
If Kenney was really interested in accountability he would have informed MPs, said Liberal defence critic Joyce Murray.
"Reports that the minister would disclose this on a call, and not in the House, reinforces how little regard he and his government have for our Parliament and its role in maintaining oversight," Murray said.
The estimates also keep secret the cost of Canada's contribution to NATO's reassurance mission in the new budget year. Those figures were not released on Wednesday.
Dave Perry of the Canadian Defence and Foreign Affairs Institute said it's the first — and only — time in nearly 20 years that cost estimates for an international operation was withheld because it was deemed classified.
Opposition NDP leader Tom Mulcair said the government shouldn't have to be dragged kicking and screaming towards accountability.
"The first thing Canadians are entitled to when we are in a war situation is truth, including the truth about the cost of that war," Mulcair said.
At the same time, a close examination of the budget estimates also show the age of austerity is here to stay at National Defence, with baseline budget spending to expected to drop over the long term.
Spending on the military is forecast to be six per cent lower in 2017-18 than it was when the deficit fight began, Perry said.
The reports, which lay out projected spending over several years, show Defence will get a slightly bigger baseline budget in 2016-17 of $19.2 billion, but will be cut to $18.7 billion in 2017-18, which is lower than the current forecast of $18.9 billion.
The figures are significant because the country is committed to a hot war in Iraq and Syria, and an emerging cold war in eastern Europe — both of which are not expected to be resolved any time soon, Perry said.
The defence policy "plan that's on the books now is intended to have the budget and spending grow every single year," he said. "That's not what's happening."
Kenney and others in the Conservative government have previously argued that they are spending 27 per cent more on the military than when they took office in 2006 — a figure that does not take into account the corrosive effect of inflation.
The government has also argued it has topped up the budget with extra appropriations, particularly for overseas missions.
Perry said the baseline budget is where all of the training, maintenance and preparations for those deployments are found. Those forecasts show deep cuts in readiness for all three branches of the military, made in the name of balancing the budget, will remain, he said.
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