​Canada's new finance minister is playing the classic "cupboard is bare game" with his fiscal update, which paints the government's books as in far worse shape than the Conservatives projected, his predecessor Joe Oliver says.

Finance Minister Bill Morneau delivered the accounting update Friday, projecting years of deficits to come instead of the surpluses the Conservatives had forecast — before even factoring in the Liberals' election promise to run up $10-billion deficits to stimulate the economy.

"That of course is the classic scenario when a new government comes in: 'I'm shocked, shocked! The cupboard is bare! These guys are more incompetent and profligate than I could have imagined!'" said Oliver, who was the Conservative finance minister from March 2014 until last month's election loss.

Oliver, speaking on CBC News Network, said he used an average of private-sector economists' GDP forecasts — to ensure the numbers couldn't be politically jiggered — in compiling his budget last April, which projected a $1.4-billion surplus in the current fiscal year, followed by surpluses of $1.7 billion and $2.6 billion in the following two years.

The new numbers that the Department of Finance put out Friday forecast deficits of $3 billion, $3.9 billion and $2.4 billion over the same period, based on the same tax and spending plans in the last Conservative budget.

Oliver said he wants to know the details of how that was arrived at.

"The fact is we left them with a $1.6-billion surplus," he said.

'It's how they deal with it'

That figure comes from a Finance Department release this month, part of a series of monthly updates the ministry puts out, that showed the federal government was indeed $1.6-billion in the black for the first half of the current fiscal year.

'The simple truth is that the economy has not performed as well as projected in the last budget,' Finance Minister Bill Morneau said Friday as the Liberals provided the first look at the government's books since they took power. (Adrian Wyld/Canadian Press)

But Finance officials often warn that their monthly updates can swing wildly from one statement to the next. The same release said the government racked up a $1.2-billion deficit in the month of September, the Conservatives' last full month in power, and was $2.3 billion in the red for August.

Still, Oliver said the Liberals need to come clean about some of the revenue and expense items in their numbers.

"What we're discussing is what happens in the next six months, the next half of the year. And in that half of the year, somehow the $1.6 billion disappears and we're now into a $3-billion deficit," he said. "It's important to understand what those expenditures that the new government, which is in control for the second half of the [fiscal] year, intends to incur — for what and why."

He acknowledged, however, that the global economic situation has worsened since he came out with his spring budget. The price of a barrel of oil was hovering around $55 US at the time and is now down below $42 US. China — the No. 2 destination for Canadian exports — has seen its economy slow. And predictions for Canada's economic growth have become less rosy.

"But you know, at the end of the day, every government is handed a set of cards," Oliver said, "and it's how they deal with it."

Watch the full interview with former finance minister Joe Oliver above or here.