The Conservative government will seek the House of Commons' approval to renew Canada’s military mission against ISIS for one year, and expand the current air combat mission to Syria, Prime Minister Stephen Harper says.

Harper made the announcement during a speech in the House of Commons Tuesday morning.

He proposed to expand the mission to include airstrikes on extremist positions in Syria. While he said the current mission against the terrorist group has helped stop the "territorial spread of ISIL," the group's hold still remains "substantial."

"In ISIL's view, anyone who does not accept its perverted version of religion should be killed. It is as self-evident to them as it seems insane to us," said Harper. "But it is far from an idle threat."

Both opposition parties responded to Harper's speech in the House Tuesday morning. NDP Leader Thomas Mulcair spoke first, saying Canada does not have a military role to play in the war against ISIS. Rather, he emphasized the need for humanitarian support.

"It is the height of irresponsibility for the government to decide to enter a war without a clear plan, without a clear beginning and a well-defined end. But that's exactly what the Conservatives are doing in Iraq. This government is taking Canada from mission creep to mission leap," said Mulcair.

Mulcair specifically took issue with Harper's initial promises that Canadian troops would not be directing airstrikes in Iraq or accompanying troops to the front lines. It was later revealed that the troops had done so, although there was some dispute over how close they were to the front lines. Mulcair said Harper has not earned the trust of Canadians to extend the current mission.

"It's simply unconscionable that this Conservative government would ask for the authority to extend the mission in Iraq when so many things they've told Canadians about the mission up until now have been false," said Mulcair.

In January, the Canadian Forces revealed that troops had been involved in firefights with ISIS. And the death of Sgt. Andrew Doiron on March 6 heightened opposition concerns even more.

Liberal Leader Justin Trudeau also told the House that his party will oppose the motion.

"Involvement in direct combat in this war does not serve Canada's interests, nor will it provide a solution to the catastrophic humanitarian crisis in this region," said Trudeau. "We will not support this government's decision to deepen this combat mission and expand it into Syria."

Trudeau called for transparency, saying that the Conservative government has "been steadily drawing Canada deeper into a combat role in Iraq." He also accused the government of having no exit strategy.

The Liberal's position on the motion was a highly-anticipated one. For weeks leading up to Tuesday, the party refused to comment on extension and expansion of the mission until it saw the government's motion.

Canada joins U.S. in Syria air war

Tuesday's motion would make Canada the only western nation to join the U.S. in the air war over Syria.

And like the U.S., Canada will notify Syria about airstrikes into its territory, but will not seek the approval of Syrian President Bashar al-Assad before ordering the strikes.

Hours after Harper announced the motion Tuesday, he faced heavy criticism from the Official Opposition during Question Period for the legal basis of bombing in Syria.

"What is the Prime Minister of Canada basing himself on? What is the legal authority for bombing in that country?” asked Mulcair.

In response, Harper cited the legal basis under which allies have been bombing Syria without Assad's approval.

"As our allies have indicated, they are taking necessary and proportionate military action in Syria on basis that the government of Syria is unwilling or unable to take prevent ISIL from staging operations and conducting attacks there, including ultimately attacks that include this country as a target," said Harper. "That is the legal basis on which we are proceeding."

Mulcair later told CTV’s Power Play that Canada’s involvement in Syria will be “assisting” Syrian President Bashar al-Assad, whom he called a “war criminal.”

But Defence Minister Jason Kenney said Canada is not helping Assad.

“To the contrary,” he told Power Play.”Assad has demonstrated that he’s either unwilling or unable to control the menace of ISIL in his own territory.”

There are currently 600 Canadian Forces members in support roles in the region, along with six CF-18s, two Aurora patrol aircrafts and a C-150 Polaris.

There are also 69 Canadian special forces members serving as military trainers in northern Iraq – but sources told CTV's Ottawa Bureau Chief Robert Fife they will not be part of the action into Syria.

Nor will Canada send commandos to laser guide air strikes in Syria.

The current six-month mission is set to end on April 7. Kenney, who called ISIS a “genocidal terrorist organization,” said the risk of operating in Syria is “modest” and the mission against Islamic State is being supported by all NATO allies in some shape or form.

May denied chance to speak

Meanwhile, Green Party Leader Elizabeth May was denied the chance to speak about the ISIS mission in the House of Commons Tuesday. She said that Conservative MPs refused to consent to her making a statement.

May later told Power Play that the Conservatives’ plan to expand the military mission is “a mess.”

“Now we have this bizarre spectacle that, without any international law on our side, we are going to start bombing into Syria -- which, under any international law is illegal -- and we’re going to be bombing the rebel forces that are against Bashar al-Assad, whom we agree is a brutal dictator, but it happens that … they’re also ISIS, whom we’re trying to eradicate,” she said.

“This is a mess. And interfering in a civil war of sectarian violence of such enormous degrees of complication is very likely to make things worse.”