Canadian Prime Minister Mark Carney has avoided major errors in a French debate that tested his occasionally shaky language skills as the election front-runner sought to parry attacks from his conservative opponent.

Carney, who leads Canada's Liberal Party, has at times struggled to articulate his positions in French while campaigning ahead of the April 28 vote, and needed to show during the debate on Wednesday that he was proficient enough to lead the bilingual nation.

After an uncertain start, Carney appeared to grow increasingly comfortable on a night that saw him face sustained attacks from Conservative Party leader Pierre Poilievre, a fluent French speaker.

Carney, who took over as prime minister from Justin Trudeau on March 14, tried to reaffirm the core message of his campaign: that his experience as a central banker during periods of economic upheaval make him the ideal choice to confront US President Donald Trump.

Trump has unleashed a trade war on Canada and incensed the northern neighbour with repeated talk of annexation and making it a 51st state.

"Our relations with the Americans have changed everything, we have to act," said Carney, whose Liberals are leading the Conservatives in most opinion polls.

Poilievre has also promised to stand firm against Trump but argued that a decade of weak economic performance under the Trudeau-led Liberals left Canada vulnerable to hostile US trade policies.

While conceding that "no one can control Donald Trump's decision," the Conservative Party leader pledged to "put Canada first."

Poilievre continued his effort of trying to tie Carney to Trudeau – who became deeply unpopular toward the end of his decade in power.

He suggested Carney should be "embarrassed to ask Canadians for a fourth mandate despite a terrible Liberal record."

"I'm not Justin Trudeau," Carney replied. "I just got here."

The leader of the left-wing New Democratic Party, Jagmeet Singh, and the head of the Quebec separatist Bloc Quebecois, Yves-Francois Blanchet, were also on stage.

But in a departure from past Canadian elections, the influence of the smaller parties could be diminished, with polls indicating this year's race is largely becoming a two-party contest.

Wednesday's debate was entirely in French. An English-language debate follows on Thursday.

In a distinctly Canadian decision, Wednesday's debate was moved up two hours to minimise a scheduling conflict with the final regular season game of the Montreal Canadiens hockey team, a cherished Quebec institution. (AFP)