Newly elected Liberal Leader Justin Trudeau will face his first test when he appears in question period on Monday, after MPs return to Ottawa following a two-week stretch in their ridings.

All eyes will be on how well the young Trudeau, the eldest son of former prime minister Pierre Elliott Trudeau, performs against Prime Minister Stephen Harper, who is expected to be in the House.

In an interview airing Sunday with CBC News anchor Peter Mansbridge, Trudeau said his first question to Harper would be about some of "the many concerns" that have come up during the course of the five-month leadership race.

Trudeau’s first face-off with Harper came in March when the Quebec MP replaced interim Liberal Leader Bob Rae during question period.

Harper found himself tongue-tied when he referred to Trudeau as a "minister" rather the member from Papineau.

Trudeau conceded to Mansbridge that he was nervous because it was his first question to the prime minister, but quickly added that Harper's nervousness was "a source of some speculation and amusement."

Although Trudeau did not hold a press conference Sunday after winning the leadership, he will face reporters for the first time as Liberal leader in a scrum after question period on Monday.

Another test for the new Liberal leader will come with a byelection in the riding of Labrador on May 13.

Liberals are hoping to regain the seat they lost to the Conservatives by 79 votes in the last federal election.

The seat was vacated by former Conservative minister Peter Penashue last month, after he acknowledged his campaign accepted ineligible donations during the 2011 election.

If there was any doubt Trudeau will have to face attack ads, the Conservative Party did not waste any time pointing out his lack of leadership experience — giving the new leader a hint of what future attacks could look like.

"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," the written statement said moments after the results were announced on Sunday.

Trudeau ‘surprised’ by landslide

Trudeau's message, in his victory speech, was one of unity and hope with an eye to the next election in 2015.

Vowing to usher in a "younger, more hopeful, less negative" kind of politics, Trudeau signalled his intent to put an end to an era of internal party divisions.

"I don’t care if you thought my father was great or arrogant. It doesn’t matter to me if you were a Chrétien-Liberal, a Turner-Liberal, a Martin-Liberal or any other kind of Liberal. The era of hyphenated Liberals ends right here, tonight."

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Justin Trudeau, his wife, Sophie Grégoire, son Xavier and daughter Ella-Grace celebrate after he was elected new leader of the Liberal Party with 80 per cent support in Ottawa on Sunday. (Christinne Muschi/Reuters)

Trudeau told Mansbridge he was "surprised' by his landslide win and credited his campaign team for getting out the vote.

"It feels pretty good," a beaming Trudeau said.

Trudeau was elected through a preferential ballot based on a points system that gave each of the 308 ridings in the country 100 points, for a total of 30,800 points.

Trudeau received 80 per cent support or 24,668 points — he only needed to obtain 50 per cent plus one, or a total of 15,401 points.

MP Joyce Murray came in second, as expected, with 3,130 points, while former Toronto-area MP Martha Hall Findlay came in third with 1,760 points.

Former cabinet minister Martin Cauchon was fourth with 815 points, Toronto lawyer Deborah Coyne fifth with 214 points, and former retired military officer Karen McCrimmon sixth with 210 points.

The total turnout for the vote was 82 per cent after 104,552 people cast a ballot by the time polls closed on Sunday afternoon, out of a total of 127,264 registered voters.

That's the largest number of people to elect a leader in the history of Canada, party officials told Liberals moments before announcing the results.

The supporter category has been an experiment for the Liberals, who wanted to inject new life into the party after being reduced to third-party status in the House of Commons after the last federal election.

Supporters voted for the new Liberal leader without joining the party as permanent members and without paying a membership fee.

Almost 300,000 supporters initially signed up to take part in the leadership race but in the end just over 40 per cent of them actually registered to vote.

While final fundraising results have yet to be posted, Trudeau had previously reported he'd brought in almost $1.1 million from some 8,500 donors.

Murray is said to have pulled in the second largest sum, with $250,000 from more than 2,200 contributors, her campaign told CBC News.

Hall Findlay and Cauchon both told CBC News they are now or soon to be "debt-free."