The Conservatives are accusing the Liberal government of bad economic management and broken promises, after the finance minister said he expects a deficit of at least $18.4 billion in the next fiscal year, not including billions in planned infrastructure spending.

That $18.4 billion figure is almost double what the Liberals campaigned on last fall. Prime Minister Justin Trudeau had said he would run “modest deficits” of no more than $10 billion per year over three years.

Interim Conservative leader Rona Ambrose said during question period in the House of Commons Monday that Liberals “frittered away a surplus” after less than 100 days in office, pointing to finance department numbers she said showed the Conservatives left office with a billion-dollar surplus.

The prime minister responded that “investment” will boost the economy and that Canadians elected his government to make such investments, after 10 years during which the Conservatives “didn’t create the necessary growth.”

Trudeau also said that the Tories “fudged the numbers” and “the reality is, they left us a deficit.”

NDP Leader Tom Mulcair later demanded to know whether some of the deficit spending will go to upping employment insurance benefits for laid off workers. The prime minister said, “yes” his government will “strengthen the EI system.”

Trudeau also took a shot at the NDP leader, saying that Mulcair had campaigned on balancing the budget, “which means right now he’d be cutting billions and billions from the Canadian economy.”

In his fiscal update Monday morning, Finance Minister Bill Morneau said the federal budget will be unveiled on March 22.

Morneau said that in addition to the $18.4-billion deficit expected in 2016-17, Ottawa is forecasting a $15.5 billion deficit in 2017-18 -- more than six times higher than the previous estimate of $2.4 billion.

However, Morneau said that cutting back on spending plans to rein in the deficit would be “wrong,” adding, “I’m talking about investments, not spending.”

“I won't have budget 2016 simply become a knee-jerk reaction to recent economic shifts,” he said. “We'll be acting out of reason."

Morneau also said that he’s “not considering any tax changes at this time” in order to reduce the deficit.

The economic downturn is expected to wipe out more than $61 billion from the federal treasury.

The revised outlook is based on the average projected oil price of $40 for 2016, down from $54 in the government's fall update. The projected growth is also down to 1.4 per cent, from two per cent in the fall.

Because the global oil market is over-supplied, declining oil prices may not rebound as quickly as previously expected. In the meantime, the loonie is expected to hover around 72 cents U.S.

There are also expectations that U.S. economic growth “may again disappoint” in 2016, and negatively affect Canadian exports, as well as incentives to expand the energy sector.

Morneau said the government wanted to be “open and transparent” about the state of the economy by releasing the new figures ahead of the budget. He said there’s “no question that times are tough” and acknowledged that it will take longer than promised to reach a balanced budget.

During the election campaign, the Liberals had promised to balance the books by 2019.

Earlier in the day, interim Conservative leader Rona Ambrose called the government’s budget plan “a recipe for waste and mismanagement.”

She said the Liberals broke a “significant election promise” by exceeding their deficit promise with a “reckless” and “irresponsible” spending plan.

Ambrose called on Morneau to get spending under control and introduce more “business-friendly” measures, such as ratification of the Trans-Pacific Partnership trade deal.

Although the Conservatives say now is not the time for deficits, they inherited a surplus from the Liberals in 2006 and ran deficits from 2008-09 until last year’s balanced budget. The deficit peaked at $55.6 billion, during the recession of 2009-10, according the finance department.

Conservative finance critic Lisa Raitt later told CTV’s Power Play she suspects the Liberals will be creating a “structural deficit,” as opposed to “the kind that stimulates the economy.”

NDP finance critic Guy Caron, meanwhile, told Power Play his party is not opposed to “smart spending” on things like employment insurance, increasing the Guaranteed Income Supplement cheques mailed to low-income seniors, or cutting taxes for those making as little as $11,000 per year.

Caron argued those measures would stimulate the economy because the recipients would spend the cash, while the Liberals’ current tax cuts are going mostly to those making more than $90,000 per year, and they might not spend it.

Caron also advocated for a corporate tax increase, which the NDP had said during the campaign would help balance the budget.

François-Philippe Champagne, Parliamentary Secretaryto the Minister of Finance, was asked whether the projected deficit amounts to a broken campaign promise.

“Canadians should feel more confident than ever because we’re open and transparent,” he told Power Play. “What we said to Canadians today is that what you voted for is exactly what we deliver.”

With files from The Canadian Press