NDP Leader Jagmeet Singh won a critical Burnaby South byelection Monday night, finally allowing him to lead his party from within the House of Commons.

In his victory speech, Singh thanked supporters and promised to fight against poverty and continue his party's campaign for a universal pharmacare plan.

"And when I take my seat in the House of Commons, I will work hard to make you all very proud," Singh said.

Singh's win came in one of three federal byelections held Monday in B.C., Ontario and Quebec.

In Ontario's York—Simcoe riding, Conservative candidate Scot Davidson claimed victory, stepping into a seat long held by retired Conservative MP Peter Van Loan.

In the Montreal riding of Outremont, Liberal Rachel Bendayan won her campaign, taking control of a seat last held by former NDP leader Thomas Mulcair.

Results from Burnaby South in B.C., show Singh claimed victory with 39 per cent of the vote. The Liberals followed with 26 per cent, followed by the Conservatives with 22.5 per cent. Former Conservative MP Maxime Bernier's People's Party of Canada trailed with 10.6 per cent.

Singh also pledged to help the NDP "reconnect" with Quebec voters who have drifted away, in an effort to realize the political ambitions of the party's late leader, Jack Layton.

"We are the champions for Quebecers. New Democrats are the champions for Canadians, we will continue to do that work."

Low turnout

The Conservatives secured their seat in the Ontario riding of York—Simcoe with 53.2 per cent of the vote to the Liberals' 29.9 per cent and the NDP's 7.4 per cent with 115 of 136 polls reporting.

Early numbers showed that turnout in all three byelections was low: just over 19 per cent in York—Simcoe and just over 18 per cent in Outremont. Burnaby South drew slightly larger numbers at 29 per cent, but all three fell below the average of the last 20 years which sits at just under 35 per cent for byelections.

Watch as Jagmeet Singh declares victory:

NDP Leader Jagmeet Singh says Canada can make different choices and get better results 1:59

In Outremont — where the NDP was looking to hold on to the seat of the party's former leader — Bendayan claimed victory with 40 per cent of the vote. The NDP trailed with 26.1 per cent, followed by the Greens and then the Bloc Québécois.

"On behalf of Liberals across Canada, I want to congratulate Rachel Bendayan and her team on their hard-earned victory, and I know that she will be a dedicated voice for Outremont in Parliament," Suzanne Cowan, president of the Liberal Party of Canada, said in a statement.

Vancouver NDP MP Jenny Kwan acknowledged the loss of Outremont was "a disappointment."

"What we're going to do, of course, is learn from this experience and then we're going to redouble our efforts to ensure that the people of Quebec know we are there for them," she said at Singh's victory party.

Liberal candidate Rachel Bendayan addressed supporters after winning the by-election in the Montreal riding of Outremont on Monday. (Paul Chiasson)

The NDP has struggled since Singh became leader in 2017. The party now sits at 14 per cent nationally, 11 per cent in Quebec and 16 per cent in B.C., according to CBC's poll tracker.

Julia Sanchez, a former international development executive, was the NDP's candidate in Outremont. Bendayan, a lawyer and former party staffer, ran against Mulcair in the last election, finishing second with 33.5 per cent of the vote to Mulcair's 44 per cent.

Conservatives win York—Simcoe

While the Conservatives usually have a tough time winning when the NDP is in a weakened position, the party kept its seat in York—Simcoe, Ont., formerly held by Peter Van Loan.

The former leader of Stephen Harper's government in the Commons, Van Loan stepped down from his seat in September and announced he was retiring from politics.

Conservative candidate Scot Davidson won the byelection in the Ontario riding of York-Simcoe. (CBC)

Van Loan won York—Simcoe in the 2015 federal election with more than 50 per cent of the vote to the Liberals' almost 38 per cent.

Davidson, a businessman, beat out Liberal candidate Shaun Tanaka, a geography professor at Queen's University and the University of Toronto, who also ran for the Liberals in the 2015 electio​n.

In his victory speech, Davidson thanked supporters and told them he is going to Ottawa to be a MP for everyone. He said he is the type of guy who is eager to meet with new constituents face-to-face to hear their concerns.

The breakaway People's Party of Canada, created last summer by Bernier, faced its first electoral test in the byelections. Results suggest it could be a spoiler that deprives the Conservatives of victory in tight contests come the fall.

While the fledgling party won less than two per cent of the vote in Outremont and York—Simcoe, it did surprisingly well in Burnaby South, where Laura-Lynn Tyler Thompson won more than 10 per cent of the vote after running on a "Canadians first" campaign that was denounced as anti-immigration and racist by some supporters of rival candidates.