Canada's Trudeau goes on attack in debate as he seeks to revive campaign

Canadian Prime Minister Justin Trudeau, trying to revive his electoral fortunes after the emergence of embarrassing photographs, used the first televised campaign debate on Wednesday to launch repeated attacks on his main rival.

Polls suggest Trudeau's left-leaning Liberals could lose power to the opposition Conservatives of Andrew Scheer on October 21 amid voter unhappiness with images of Trudeau in blackface, as well as other scandals.

Trudeau, variously interrupting and talking over Scheer, took the offensive from the start during the French-language debate in the politically important province of Quebec.

He first suggested Scheer would be open to reviving the debate on abortion.

"Do you - as a party leader, as a father and a husband - believe women should have a choice?" Trudeau asked Scheer.

There are few restrictions on abortion in Canada and the Conservatives have traditionally steered clear of the topic, fearing they could alienate progressive voters.

"Quebecers can be confident that a Conservative government led by me will not reopen this debate," Scheer responded.

Jagmeet Singh of the left-leaning New Democrats and Yves-Francois Blanchet of the separatist Bloc Quebecois - the other two leaders in the debate hosted by private channel TVA - also criticized Scheer on the issue.

"We are seeing that three of us are aligned on values, the values of Quebecers, and we have a fourth, a Conservative party that is not aligned ... on the rights of women," said Trudeau.

French is the predominant language in Quebec, Canada's second-most populous province that accounts for 78 of the 338 seats in the federal House of Commons.

The Liberals had been confident of adding to the 40 Quebec seats they won in 2015 but now face a challenge from the Conservatives as well as the Bloc, which wants independence for the province of 8.4 million people.

Scheer, whose French is the least fluent of the four leaders, sometimes stumbled over his words and on occasion looked flustered. The Conservative chief, who says Canadians are most interested in tackling the high cost of living, later accused Trudeau of planning to raise taxes.

After Scheer accused Trudeau of harbouring a secret agenda to decriminalize all drugs, the Liberal leader replied: "Again, we see the politics of fear that you are promoting."

The exchanges were the first between the leaders of the major parties since the blackface photos emerged last month, temporarily derailing Trudeau's campaign.

None of the leaders mentioned the blackface incident.

TVA has the biggest audience of any news channel in Quebec. The Canadian Broadcasting Corp will host an English-language debate on October 7 and another French-language session on October 10.