Finance Minister Bill Morneau is set to face a marathon grilling after his department confirmed that federal finances slipped back into deficit for the 2015-16 fiscal year.

Mr. Morneau is scheduled to defend his budget bill on Monday afternoon before the House of Commons finance committee. Later that evening, he will face up to four hours of questions on the floor of the House of Commons.

Every year, the Official Opposition can select two ministers to go through extended questioning in the House, and the Conservatives have chosen Mr. Morneau as one of them. The minister is also planning to attend Question Period on Monday, which would mean the possibility of nearly six hours of opposition questions in a single day.

Story continues below advertisement

On Friday, Mr. Morneau's department reported that Ottawa posted a $9.4-billion deficit in March, leading to a $2-billion deficit for the year. Finance Canada notes that further accounting adjustments – including a $3.7-billion entry for veterans' benefits – will lead to a larger deficit when the final numbers are recorded in the fall.

The department's monthly tracking of revenue and expenses – known as the Fiscal Monitor – has been the source of a politically charged debate between Conservatives and Liberals over the state of federal finances. The Conservatives were in power for slightly more than half of the fiscal year and had promised during the 2015 election campaign to deliver a second consecutive surplus.

The Liberals were elected with a platform that rejected a focus on balanced budgets, promising to run deficits for several years in an effort to boost economic growth.

Conservative MP and finance critic Lisa Raitt said the numbers show the Conservatives could have delivered on the second consecutive surplus by holding the line on spending. She said she is looking forward to the opportunity to challenge the minister during what she is calling "Morneau Monday."

"They actually don't have a handle on what they're planning to do, and the minister's going to have to be accountable for that," she said.

Mr. Morneau's March 22 budget projected a final deficit number for 2015-16 of $5.4-billion, followed by a $29.4-billion deficit in 2016-17 and a $29-billion deficit in 2017-18. Finance Canada's report on Friday indicates that the final numbers for 2015-16 are likely to be close to what was projected in the budget.

The minister's spokesperson, Daniel Lauzon, said in an e-mail Friday the numbers support what the minister has long been saying.

Story continues below advertisement

"The Conservatives have always talked a big game when it comes to balancing the budget, but their legacy amounts to them leaving behind tens of billions in additional debt with little more than a slowing economy to show for it," he said.

For the year as a whole, Friday's report shows federal expenses totalled $291.6-billion – a 5.6 per cent increase over the year before – while total revenues were $289.6-billion, a 3.8 per cent increase.