OTTAWA (AFP) - Canada's beleaguered Liberal Party on Sunday chose Justin Trudeau, eldest son of late prime minister Pierre Trudeau, as its new leader as it seeks to rebound from a major defeat at the polls in 2011.

The 41-year-old former French teacher won by a landslide, getting 80 percent of the vote, the party announced during a meeting in Ottawa. He was greeted by chants of "Justin time" from supporters.

The party's last leader, Michael Ignatieff, resigned in the wake of the 2011 drubbing, which saw the Liberals - who held power for most of the last century - relegated to the political margins as the country's number three grouping.

In his victory speech, delivered in French and English, Trudeau thanked his supporters for the confidence they placed in him, called for party unity and vowed to engage in "positive politics." But he immediately launched an attack on Prime Minister Stephen Harper and his ruling Conservatives, accusing them of readying a negative campaign.

The Conservatives "are afraid," said Trudeau.

"It is not my leadership that Mr Harper fears, it is yours: engaged and informed Canadian citizens." The Conservatives were also quick to go on the offensive.

"Justin Trudeau may have a famous last name, but in a time of global economic uncertainty, he doesn't have the judgment or experience to be prime minister," said party spokesman Fred DeLorey.

Mr Trudeau was elected to the House of Commons in 2008 and re-elected in 2011.

Liberals hope his youth and famous name can revitalise the party in time to challenge the Conservatives in the next election, likely in 2015.

In 2011, the Liberals won just 35 out of 308 seats in parliament.

According to a recent Nanos poll, the Liberals have reached 35.4 percent support nationwide, ahead of the Conservatives with 31.3 percent and the main opposition party, Thomas Mulcair's New Democratic Party, at 23.6 percent.

The Trudeau family is often compared to the Kennedys in the United States.

Mr Pierre Trudeau, who died in 2000, was prime minister from 1968 to 1979, and again from 1980 to 1984. He is considered the father of modern Canada.

He was admired for the force of his intellect and praised for his political acumen in preserving national unity against separatists from French-speaking Quebec province, as well as in establishing the Charter of Rights and Freedoms.

Mr Trudeau also decriminalised homosexuality and pushed for the bilingualism and multiculturalism that have become an integral part of the national identity.