Canadian Prime Minister Mark Carney's Liberals could soon form a slim majority in the House of Commons if the party is able to make gains in three by-elections being held on Monday.

The outcome of the races, two in the Toronto-area and one near Montreal, could solidify his hold on power, staving off a federal election until as late as 2029 and giving his party the ability to pass legislation without relying on support from opposition benches.

Liberals currently hold 171 of the 343 seats in the House, one shy of a technical majority.

The likely power shift comes a year after Carney became prime minister, and follows a series of defections by opposition members of Parliament to the Liberals.

The Liberals are widely expected to win the two Toronto ridings, or constituencies, of Scarborough Southwest and University-Rosedale.