Winning in Quebec seems to be getting harder for the federal NDP — which is why leader Jagmeet Singh is vowing to roll up his sleeves and get to work as a byelection approaches in the riding held by the party's former leader.

Speaking to CBC Radio's The House on Thursday, Singh acknowledged that the outcome of Monday's byelection in Chicoutimi-Le Fjord — which saw the Conservative candidate claim the seat — was a blow to his party, which once dominated the federal landscape in Quebec.

The NDP vote suffered an almost total collapse in Chicoutimi-Le Fjord, pulling in just 8.6 per cent of the vote after winning the riding with 37.7 per cent in 2011 and narrowly losing in 2015 with 29.7 per cent of the vote.

"The results are disappointing," Singh said.

"It means that we've got to make sure that we work really hard in Quebec and I'm committed to doing that."

Tom Mulcair's riding up next

With one Quebec byelection over, the NDP is turning its attention to the next one in the fall — in former NDP leader Tom Mulcair's seat in Outremont.

That Montreal seat — a splash of orange in a sea of Liberal red — became the cornerstone of the NDP's success in the 2011 election when Mulcair snatched it from Liberal control in 2007.

Singh didn't rule out the possibility of running in that riding, as he currently doesn't hold a seat in the House of Commons, but said there are many factors to consider as he decides where to run.

He acknowledged Outremont has "significant history" for his party, given Mulcair's success.

Earlier in the week, Mulcair had some words of warning for the party as he wraps up his political career: Start worrying.

"I am worried about a score like that, what it means for the future, no doubt," Mulcair told host Vassy Kapelos on CBC News Network's Power & Politics on Wednesday.

Former NDP Leader Tom Mulcair ends his time as an MP to become a professor at Universite de Montreal 1:42

The NDP finished in third and fourth place in the past two Quebec byelections — quite a change from its strong second-place showings in the last general election.

"All seats in Quebec, any time we've had a great showing, means it's an important region," Singh said.

Tax havens, relations with the U.S. and regulating web giants like Netflix are all issues that have troubled Quebec voters, and Singh said those are the subjects on which the party will focus going forward.

"There's issues that have resonated with people in Quebec and we're going to continue to double down on those issues."

When asked about a recent Radio Canada report about the Liberal Party attempting to convince NDP MPs to cross the floor, Singh said that his caucus members said no.

Trans Mountain a 'violation' of government promises

Singh also spoke to The House about his opposition to the Trans Mountain pipeline expansion.

Last month, the federal government announced its intention to buy the pipeline from Kinder Morgan for $4.5 billion.

The NDP leader said he'd always been opposed to the project because of what he sees as problems with the consultation and environmental review processes, but the bid to nationalize the pipeline was the last straw.

"The turning point was when the government decided to use public resources. And that, to me, is completely a violation of the commitments of this government."

Singh said he initially avoided weighing in on the dispute, as British Columbia and Alberta — the two provinces the pipeline runs through — are both led by NDP premiers.

An unsafe third country?

Immigration issues also have been a hot topic for Singh's party during this session of Parliament.

New Democrats have called for the suspension of the Safe Third Country Agreement (STCA) with the United States, which forces migrants to claim asylum in the first 'safe' country they land in.

Singh and his caucus renewed their calls for a suspension of the STCA after the U.S. started separating illegal migrants from their children at the border as part of a widely-condemned "zero tolerance" strategy.

NDP Leader Jagmeet Singh says the treatment of children torn from their parents is heinous, and that the safe third country agreement should be suspended. 1:12

"If that does not clearly indicate that the United States under the Trump administration is no longer a safe country for asylum seekers, I don't know what will," he said.

Singh said Canada has a responsibility to act — although he didn't say what actions he would take beyond suspending the STCA.