New Democratic Party leader Jagmeet Singh, who has been helping keep Trudeau in office, said he would present a formal motion of no-confidence after the House of Commons elected chamber returns from a winter break on January 27.
If all the opposition parties back the motion, Trudeau will be out of office after more than nine years as prime minister and an election will take place.
Justin Trudeau failed in the biggest job a Prime Minister has: to work for people, not the powerful.— Jagmeet Singh (@theJagmeetSingh) The NDP will vote to bring this government down, and give Canadians a chance to vote for a government who will work for them. pic.twitter.com/uqklF6RrUXDecember 20, 2024
A string of polls over the last 18 months show the Liberals, suffering from voter fatigue and anger over high prices and a housing crisis, would be badly defeated by the official opposition right-of-centre Conservatives.
The New Democrats, who like the Liberals aim to attract the support of centre-left voters, complain Trudeau is too beholden to big business.
"No matter who is leading the Liberal Party, this government's time is up. We will put forward a clear motion of non-confidence in the next sitting of the House of Commons," Singh said.
The leader of the Bloc Quebecois, a larger opposition party, promised to back the motion and said there was no scenario where Trudeau survived.
The Conservatives have been calling for an election for months.
A few minutes after Singh issued his letter a smiling Trudeau, under growing pressure to quit after the shock resignation of his finance minister this week, presided over a cabinet shuffle.
Trudeau's office was not immediately available for comment.
Votes on budgets and other spending are considered confidence measures.
Additionally, the government must allocate a few days each session to opposition parties when they can unveil motions on any matter, including non-confidence.
Before Singh made his announcement, a source close to Trudeau said the prime minister would take the Christmas break to ponder his future and was unlikely to make any announcement before January.
Liberal leaders are elected by special conventions of party members, which take months to arrange.
Singh's promise to act quickly means that even if Trudeau were to resign now, the Liberals could not find a new permanent leader in time for the next election.
The party would then have to contest the vote with an interim leader, which has never happened before in Canada.
So far around 20 Liberal legislators are openly calling for Trudeau to step down but his cabinet has stayed loyal.
The timing of the crisis comes at a critical time, since US President-elect Donald Trump is due to take office on January 20 and is promising to impose a 25 per cent tariff on all imports from Canada, which would badly hurt the economy.
The premiers of the 10 provinces, seeking to create a united approach to the tariffs, are complaining about what they call the chaos in Ottawa.