What are the ways forward for Canada as support for PM Justin Trudeau continues to falter?

Justin Trudeau's support within his own party has appeared to falter further. (AP: Darren Calabrese)

The head of a Canadian political party that has been keeping Prime Minister Justin Trudeau in power says he will vote in favour of a motion of no-confidence, effectively assuring the Liberals will be removed from power early next year.

New Democratic Party leader Jagmeet Singh said he would present a formal motion of no-confidence after the House of Commons returns from a winter break on January 27.

The prime minister has been under increasing pressure to quit since Deputy Prime Minister Chrystia Freeland resigned over a policy clash.

Mr Trudeau's support within his own party has appeared to falter further, as former loyalists said growing numbers of Liberal caucus members wanted the premier to resign.

Anthony Housefather, a Liberal member of parliament from the province of Quebec, told the CBC on Sunday that "the prime minister needs to go".

"We're in an impossible situation if he stays," Mr Housefather said, arguing the party would be hammered in an election that amounted to a referendum on Trudeau's leadership.

Democratic Party leader Jagmeet Singh said he would present a formal motion of no-confidence (AP File: Nathan Denette/The Canadian Press)

If all the opposition parties back the motion, Mr Trudeau will be out of office after more than nine years as prime minister and an election will take place.

Before that potential election though, there are a few different ways forward for Canada.

Can the PM be forced out by his Liberal party?

Not exactly.

The Liberal leader is selected by a special convention of members within the party.

There is therefore no formal party mechanism to remove Mr Trudeau if he wants to stay.

That said, if members of his own cabinet and a large number of legislators call for him to go, he may conclude his position is untenable.

A resignation would breach new ground

Trudeau faces leadership test as deputy PM resigns over tariffs spat

Photo shows A man in a blue suit and black hair holds a microphone

Chrystia Freeland, who is also finance minister, left cabinet on Monday after clashing with Mr Trudeau on issues including how to handle possible Trump tariffs.

If Mr Trudeau resigns, the Liberals will name an interim leader to take over as prime minister while the party sets up a special leadership convention.

These conventions usually take months to arrange and if an election does occur before then, the Liberals would be in the hands of a prime minister not chosen by members. 

This has never happened in Canada.

The Liberals could try to run a shorter convention than usual, but this might prompt protests from candidates who felt this placed them at a disadvantage.

It is important to note there is no way the deputy prime minister could quickly be named prime minister on a permanent basis, since tradition dictates that the interim leader does not run as a candidate to lead the party.

Public Safety Minister Dominic LeBlanc was named as Ms Freeland's replacement following her resignation.

Prime Minister Justin Trudeau (right) congratulates Dominic LeBlanc. (AP: Justin Tang/The Canadian Press)

Could Canadian parliament kick the PM out?

Canadian governments must show they have the confidence of the House of Commons elected chamber. 

Votes on budgets and other spending are considered confidence measures and if a government loses one, it falls.

In nearly all cases, an election campaign starts immediately.

The House of Commons closed for the winter break on Tuesday and does not return until January 27.

The House of Commons closed for the winter break. (Reuters: Blair Gable)

The government can use procedural manoeuvrers to avoid being brought down on a spending measure but it must allocate a few days each session to opposition parties when they can unveil motions on any matter, including no-confidence.

Assuming the government allocates the opposition days at the end of the session, the most likely time for Mr Trudeau to be brought down would be in the last 10 days of March. 

This would trigger an election at some point in May.

The king and governor general have ultimate power

Ultimate constitutional power in Canada lies with Governor General Mary Simon.

Governor General Mary Simon can technically oust Mr Trudeau as Canada's PM. (AP: Spencer Colby/The Canadian Press)

She is the personal representative of King Charles, the head of state. 

In theory, Ms Simon can remove Mr Trudeau from his role as prime minister. 

But in reality this is unlikely to happen.

"The governor general won't dismiss a prime minister who still holds the confidence of the Commons," said Philippe Lagasse, a professor and constitutional expert at Ottawa's Carleton University.

PM could discontinue parliament

While PM, Mr Trudeau could prorogue parliament, which would formally end the current session and give him some breathing space. 

Under this scenario, the return of the House would be delayed by several weeks, allowing the government to unveil a new plan for how it plans to run the country. 

This would have the advantage of delaying any motion of no-confidence.

However it would likely further anger Liberal legislators, especially if Mr Trudeau remains the prime minister.

Currently, Mr Trudeau trails his main political rival, Conservative Pierre Poilievre, by 20 points in public opinion polls.

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