Canadian Prime Minister Justin Trudeau's Liberal Party has retained power but a narrow election win means he is forced to lead a minority government as prime minister, the BBC reports.

His party will claim the most seats in parliament but their second term will be much harder, relying on other parties to pass legislation.

The Liberals are expected to claim 156 seats, 14 short of a majority.

His centre-right Conservative rivals are heading for 122 seats, a marked increase from the 95 it held before.

Monday, October 21 night's results could be good news for the country's left-leaning New Democratic Party (NDP) and its leader Jagmeet Singh, who could be kingmaker.

This federal election was seen as a referendum on Trudeau, who endured a bumpy first term, tainted by scandal.

"You did it my friends. Congratulations!" he told cheering supporters in Montreal.

Turning to address those across the country who voted for him, he said: "Thank you for having faith in us to move our country in the right direction."

Trudeau swept into power in 2015 promising "real change" and a slew of progressive pledges.

Now, after four years in power, Trudeau has faced criticism for his ability to follow through.

Still, according to an independent assessment by two dozen Canadian academics, Trudeau has kept - fully or partially - 92% of these promises, the most by any Canadian government in 35 years.