Updated 5.15pm with resignation announcement. 

Canadian Prime Minister Justin Trudeau announced his resignation on Monday, saying he will leave office as soon as the ruling Liberal party chooses a new leader. 

"I intend to resign as party leader, as prime minister," Trudeau, who has been in power since 2015, told reporters in Ottawa following a protracted political crisis that saw top Liberal allies urge him to quit.   

Legislative elections are scheduled to be held by the end of October.

Trudeau's popularity has waned in recent months, with his government narrowly surviving a series of no-confidence votes and critics calling for his resignation.

He faced further pressure from incoming US president Donald Trump, who has threatened a 25-percent tariff on Canadian goods.

Deputy Prime Minister Chrystia Freeland quit in December after disagreeing with Trudeau over how to respond to Trump's apparent plan, in the first open dissent against the prime minister within his cabinet.

Trudeau announced a major shakeup to his cabinet later that month, changing a third of his team in a bid to settle the political turmoil.

He travelled to Florida in November to meet with Trump at his Mar-a-Lago estate in a bid to head off a trade war.

Trudeau is trailing his conservative rival Pierre Poilievre in the polls. Photo: Shutterstock.com.

But the US president-elect has since also landed humiliating blows against Trudeau on social media, repeatedly calling him "governor" of Canada and declaring that the United States' northern neighbour becoming the 51st US state is a "great idea."

Trudeau swept to power in 2015 and led the Liberals to two more ballot box victories in 2019 and 2021.

But he now trails his main rival, Conservative Pierre Poilievre, by 20 points in public opinion polls.

The eldest son of the charismatic former prime minister Pierre Trudeau, who died in 2000, Justin Trudeau came late to politics after working as a snowboard instructor, bartender, bouncer and teacher.

He was first elected to the House of Commons in 2008 to represent a working-class Montreal neighbourhood.

He brought in Senate reforms, signed a new trade deal with the United States and introduced a carbon tax to reduce Canada's greenhouse gas emissions during his first two terms as prime minister.

The married father of three also legalized cannabis, held a public inquiry into missing and murdered Indigenous women and passed legislation permitting medically assisted suicide.