Liberal MP Justin Trudeau lost his temper and called Environment Minister Peter Kent a "piece of sh**" during question period in the House of Commons Wednesday while Kent responded to questions about the Kyoto Accord.

Canada recently backed out of Kyoto -- a move critics say severely weakens the international climate change agreement.

New Democrat environment critic Megan Leslie was questioning Kent on the decision to abandon Kyoto at the recent climate conference in Durban, South Africa.

She suggested Canada was backing out in order to hide its failure at reducing emission to Kyoto's targets, saying "the rest of the world is moving forward, building a new energy economy, but Canada is being left behind."

Kent responded: "If she had been in Durban she would have seen in fact that Canada is a leader..." before he was drowned out by Trudeau shouting "you are a piece of sh**" and the House of Commons erupting briefly into shouting.

Trudeau's comment appeared to be in defence of Leslie, a Halifax MP, who was apparently not invited to attend the Durban conference with the government's delegation.

Trudeau quickly stood up and apologized to the House of Commons and Speaker Andrew Scheer said the incident would be dealt with later.

"I lost my temper and used language that was most decidedly unparliamentary and for that I unreservedly apologize and withdraw my remarks," Trudeau said.

Kent responded by saying he wasn't offended, but suggested that Trudeau should issue an "abject apology" to the House of Commons.

The Speaker noted that Trudeau had already apologized.

Speaking on CTV's Power Play later in the day, Trudeau said his outburst was the result of Kent's "patronizing condescension" toward opposition MPs, particularly about not being in Durban, "when he and the Prime Minister's Office did everything they could to keep the Opposition away."

"So when he chided her for not attending Durban, I lost my temper, I lost my cool."

It's been a relatively foul season in Ottawa, with the Liberals' Bob Rae tweeting "bull sh*t" about an apparent feud between two young Grits this week.

Earlier this fall, NDP MP Pat Martin used an expletive on Twitter when the government shortened debate on its budget legislation.

But Trudeau said the frustration in Ottawa stems from the Conservative shut-down tactics.

"They're not giving us a voice, and that causes a lot of frustration."

NDP Deputy House Leader Joe Comartin said that Parliamentary decorum really took a nose-dive by early October after a relatively civil spring session.

"It began deteriorating almost as soon as we came back in the fall," he said, adding that the Liberals had been the "main proponents of bad behaviour" in the spring session before the May election.

"By early October, the Conservatives clearly had changed. The heckling was there, the attempts to yell down people, a lot of personal attacks," he said.

House Leader Peter Van Loan agreed that the outbursts came near the end of a busy fall session.

"There are some who are frustrated, and I understand that. Particularly for Mr. Trudeau and the opposition Liberals, who've had a very difficult time adjusting to their third-party status."

He added that with the NDP enjoying second-party status, the opposition was initially focused on policy questions instead of headline-grabbing issues.

"That's begun to slide. And they've sort of gone back to what the Liberals did before the last election: running around chasing what they think might be a scandal."