CBCnews.ca will have live coverage of question period today at 2:15 p.m. ET - as Justin Trudeau faces a grilling for the first time as prime minister from interim Conservative leader Rona Ambrose and NDP Leader Tom Mulcair. Follow it live here.

Interim Conservative Leader Rona Ambrose took sharp aim at the Liberal plan for the 42nd Parliament today, insisting it lacks a transparent costing and implementation strategy, and warning it will download a huge fiscal burden to the provinces.

Responding to the throne speech in the House of Commons, Ambrose said the roadmap shows "big, activist government is alive and well." The Liberals have delivered many promises, but few concrete plans, she said.

In his own remarks, Prime Minister Justin Trudeau confirmed his government would introduce its promised "middle-class tax cut" on Wednesday, and that the first large group of government-supported Syrian refugees would arrive this week.

Ambrose warned that Trudeau has a recipe for big spending that will lead to higher taxes, massive deficits and eventually, major program cuts.

"We will be the taxpayers' watchdog," she said.

Ambrose said the throne speech failed to address:

An economic plan.

Supports for the private sector.

A strategy for the auto, forestry and energy sectors.

Help for unemployed Albertans.

​A future role for agriculture, farming.

She praised Trudeau for revising his plan to bring 25,000 Syrian refugees to Canada by year's end, and expressed hope he would revisit other key promises, including the pledge to pull Canada's fighter jets from Iraq and Syria. Trudeau can offer "no sensible argument" for the withdrawal, she said, because "there is none."

"Canada is not back, Canada is backing away," she said.

Ambrose called it "alarming" that the throne speech made no mention of ISIS, as U.S. President Obama and other allies ramp up efforts to take on the global threat from the militant group.

"While our allies are ramping up their efforts, the prime minister has believed that posing for selfies at international conferences is a better use of his time," she said.

New tone or sharp tongues?

While all party leaders have promised to adopt a more conciliatory, constructive tone, it didn't take long for the sparks to fly.

Treasury Board President Scott Brison responded to Ambrose's critique, blasting the Conservative record in 10 years in office.

Rona Ambrose, the Conservatives' interim leader, called the Liberals' throne speech confirmation of a return to big government, and criticized the government for failing to mention the fight against ISIS, in her response to the speech on Monday. (Adrian Wyld/Canadian Press)

"How can she speak about big government when she was part of one of the biggest, most wasteful governments in Canadian history?" he asked.

Ambrose responded: "It's been 25 minutes and the sunny ways are over," in reference to a phrase used by Trudeau several times in the wake of his election on Oct. 19.

NDP Leader Tom Mulcair, who cast his party as the "progressive opposition," criticized the throne speech for failing to reference:

More oversight for intelligence agencies under Bill C-51, the Conservative anti-terror legislation.

Restoring door-to-door mail delivery by Canada Post.

Returning the retirement age to 65 from 67.

"There wasn't a word about child care," he added.

Mulcair urged the Liberal government to take quick action to close the funding gap for First Nations education, and take steps to address the "archaic" first-past-the-post electoral system that leads to "phony" majorities.

Trudeau stuck to his messages about helping the middle-class by asking the wealthy to pay more, and promising to usher in a new era in Parliament. He said Canadians are tired of the cynicism that has been a feature in Parliament for too long.

"We are committed to delivering real change in the way government works," he said. "It means setting a higher bar for openness and transparency, something needed if this House is to regain the confidence and trust of Canadians," he said.

Throne speech set out priorities

The government's agenda was laid out in an address by Gov. Gen. David Johnston that was delivered in the Senate chamber Friday. It promised a new tone for Parliament, a tax cut for the middle class and a renewed relationship with First Nations.

Other priorities for the 42nd Parliament mirror the Liberal election platform, including: