Conservative Leader Pierre Poilievre and NDP Leader Jagmeet Singh got into a heated exchange in the House of Commons on Thursday, just minutes after Singh announced his party would not be supporting the Conservatives’ first non-confidence motion against Prime Minister Justin Trudeau’s government.

“He is a fake, a phony and a fraud. How can anyone ever believe what this sellout NDP leader says in the future?” Poilievre said to Singh during question period, posing questions to Singh, rather than to any member of the government.

As he did, heckling could be heard from NDP MPs, including complaints that this question wasn’t related to government business.

In response, Singh, who sits further down on the same side of the chamber as Poilievre, yelled over to the Official Opposition leader, leading to an eruption of jeers and cheers from all sides of the House.

House Speaker Greg Fergus then paused proceedings for a few minutes in an attempt to bring order to the chamber.

Microphones were muted on the live feed from the floor of the House of Commons and cameras did not cut away from the Speaker’s chair. But, as those in the viewing galleries above the chamber could see, Singh got out of his seat and continued to address Poilievre, pointing at him from the floor.

“I would suspect, although the chair didn't hear, that there might have been some strong words which were exchanged between members,” Fergus said after the tense moment, reminding all MPs that question period is meant to hold the government accountable, not opposition parties.

“I ask members to please remember that Canadians are looking at us and let us conduct ourselves in a way really befitting of each of our constituencies and a country as a whole.”

Both leaders left the chamber soon after the exchange.

The boiling over of simmering tensions between the two leaders came shortly after Singh announced the NDP will vote to support the Liberal government in next week’s non-confidence motion vote.

The motion was already set to fail after the Bloc Québecois announced Wednesday that they will be voting against the Conservative’s attempt to force an early election.

Singh said his party’s decision to support the Liberals is about pushing back against potential Conservative cuts to programs like dental care and pharmacare.

“The decision moving forward is far too important for Canadians and for the middle class,” Singh said. “That's why we're not going to let Pierre Poilievre tell us what to do. We're not going to listen to someone who wants to cut the things that people need.”

Speaking to reporters on Thursday, Singh was repeatedly asked how he could support the Trudeau government just weeks after pulling out of his party’s supply-and-confidence deal.

“I stand by my words… Trudeau has let you down, and does not deserve another chance,” Singh said.

When asked if the NDP’s support means the party is giving Trudeau another chance, Singh said “not at all.”

“Canadians will have that decision to make when the election comes. And when that election comes, we want to make it very clear, I do not believe that Justin deserves a second chance.”

As he came out of question period, Poilievre marched to the microphone stationed in the House of Commons foyer and accused Singh of taping up his pact with Trudeau after the byelections had passed, repeating the line of attack he used in the House.

With files from CTV News' Rachel Hanes