Federal Conservative leader Pierre Poilievre is hailing a decisive British Columbia byelection victory in Cloverdale-Langley City, where Tamara Jansen has won with about two-thirds of the vote.

Monday's byelection in the Fraser Valley seat, which had been held by the Liberals and is traditionally closely contested, came on the day Prime Minister Justin Trudeau's ruling party was thrown into turmoil by finance minister Chrystia Freeland's resignation.

Poilievre congratulated Jansen in a post to social media, saying she earned "twice as many votes as all the other candidates combined."

Elections Canada says Jansen, who held the seat from 2019 to 2021, won 66.3 per cent of the vote, with Liberal Madison Fleischer a distant second on 16 per cent and New Democrat Vanessa Sharma in third with 12.5 per cent.

All three provincial ridings in Langley were won in October by B.C. Conservatives, who have no official relationship with the federal Conservatives, and Jansen's return to Ottawa marks the third seat lost by the governing Liberals in byelections this year.

Liberal John Aldag had held Cloverdale-Langley City but he resigned to run in the provincial election for the NDP in Langley-Abbotsford, where he was defeated by a B.C. Conservative.

Jansen had unseated Aldag in 2019 before a 2021 rematch saw Aldag return as MP.

Voter information cards were not sent out to constituents because of the weeks-long Canada Post strike, and Elections Canada is reporting turnout of 16.3 per cent based on pre-election enrolment.