OTTAWA - Santa cannot be amused.

The last hours of the House of Commons this calendar year were marked not by expressions of holiday cheer, but with naughty MPs hurling insults and expletives like dirty snowballs.

It's the end of a parliamentary session where decorum has been on a steady, downward slide. Opposition MPs and Conservatives traded rhetorical grenades concerning everything from government-imposed limits on legislative debate to disputes over how to combat climate change.

Environment Minister Peter Kent attracted the latest icy nor'wester during Wednesday's question period when he chided NDP critic Megan Leslie for being ill-informed about last week's climate-change conference because she hadn't attended. In fact, the government blocked the opposition from attending the UN conference in Durban, South Africa, as part of the Canadian delegation.

Kent's putdown prompted a clearly audible outburst by Liberal MP Justin Trudeau: "You piece of (expletive)!" he yelled across the aisle.

The comment created a furor, with Conservatives angrily shouting back at Trudeau as the House erupted. His father, former Liberal prime minister Pierre Trudeau, had once wryly claimed to have mouthed the words "fuddle duddle" in the Commons and not a profane phrase with a similar ring.

Trudeau the younger owned up to his cussing and unreservedly apologized in the Commons. Later, he told reporters it's all a sign of the times on Parliament Hill.

"Why did I stick up for someone from a party outside of mine?" Trudeau said.

"I know the frustration that Miss Leslie went through but I saw first-hand the frustration that Kirsty Duncan, our environment critic, went through as she tried to figure out a way to go to Durban independently, without accreditation, without help from the government, to try and represent to the world that Canada is not being well represented by this current minister of the Environment and this government."

Leslie, who was criticized last month for calling Natural Resources Minister Joe Oliver a "grumpy old man," said opposition MPs simply live in frustrating times. The NDP has been called traitorous and treacherous by the Conservatives, she noted, for travelling to Washington to speak out against the Keystone XL pipeline.

She called Trudeau's Liberal s-bomb "an honest reaction" which he quickly realized had crossed the line.

"I certainly have bit my tongue so hard sometimes it bleeds in that House," said Leslie.

She added that sometimes "the Conservatives and their games do get the better of us and we react .... I just wish that the Conservatives would actually talk about issues and stop with the name calling and these kinds of dirty tricks. It's really shameful."

But Trudeau's wasn't the only unparliamentary language used Wednesday.

NDP MP Ryan Cleary called Fisheries Minister Keith Ashfield a "bully" over the alleged muzzling of bureaucrats concerned about budget cuts in his department. Cleary had to be coaxed into retracting the statement following question period.

Earlier in the day on Twitter, interim Liberal leader Bob Rae used the social networking site to bluntly call a fellow Grit's musings on internal party politics bull feces, or words to that effect.

But this fall's best known bleeping comment was NDP MP Pat Martin's potty-mouthed paroxysm of frustration after debate on the government's budget bill was cut off: "This is a (expletive) disgrace ... closure again. And on the Budget! There's not a democracy in the world that would tolerate this jackboot (expletive)," Martin wrote on Twitter from his Commons seat.

Opposition MPs have attempted other means to express their anger over government tactics. NDP and Liberals on the Commons access to information committee, for example, refused to attend meetings after the Tories demanded the CBC table private internal documents.

The Liberals walked out of a vote in November to show their disapproval of the naming of a unilingual auditor general.

With the Commons poised to go dark until Jan. 30, the opposition is now concerned by a Tory move in one committee to make all of its discussions on witnesses, future business and other routine matters confidential.

Several sources told The Canadian Press last week that signals have been sent by the government to the Office of the Auditor General that he won't be asked to attend as many committee meetings anymore.

NDP House leader Joe Comartin said these kinds of committee deliberations have traditionally been held in public. "It’s been in public because we live in a democratic, open society."

Liberal MP Marc Garneau said the government is simply not living up to its commitment to openness and transparency.

"You know, a lot of us have said, OK, alright, maybe things are a little crazy in the House of Commons but at least we get to do some serious work in committee," said Garneau.

"Now ... this government is trying to actually close down the work in committee so that you and the public are not able to attend these."

The Liberals are also enraged by the treatment of their MP Irwin Cotler, whose constituents in Montreal have been receiving calls from a firm working for the Conservatives suggesting the longtime parliamentarian is about to step down.

Government House leader Peter Van Loan said the lack of decorum is an opposition problem.

"I think that tells you that we're at the end of a fall session and we're approaching the final days up here and as you know, some people are finding it difficult to control themselves," said Van Loan.

"That being said, on the government side we've been approaching things in a productive, workmanlike, orderly fashion to get the job done."

And so the high spirits and slight silliness of end-of-sessions past is curiously absent this December.

It was left to Foreign Affairs Minister John Baird to poke fun at the lack of seasonal spirit, rising on his own point of order after Trudeau and Cleary's post-question-period apologies.

"I would just like to wish everyone a Merry Christmas, and peace on earth," said Baird, drawing roars of laughter.

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• Careless Whisper

  However you look at Canada's 15th prime minister, it's hard not to see Pierre Elliott Trudeau as a politician cut from a very different cloth. While much of his globe-trotting, playboy image was doubtless driven by the media -- Trudeau was actually a workaholic and sleepless intellectual -- the man certainly had his moments. Luckily, the news wasn't delivered quite so relentlessly in 1971 as it is these days - or Trudeau wouldn't have heard the end of it when he told an opposition member to <a href="http://quotes4all.net/pierre elliott trudeau.html">"F-- Off".</a> Well, actually he mouthed it. And although the TV tape clearly captured his salty salute, Trudeau was allowed to tell reporters he had actually said 'Fuddle Duddle'. And that was that.

• That's Pat F--ing Martin, To You

  Outspoken doesn't seem to quite cut it when describing NDP MP Pat Martin. The man speaks out a lot. And every now and then, he brings the thunder. Like last November, when he treated his 1,400 Twitter followers to a <a href="http://www.huffingtonpost.ca/2011/11/17/pat-martin-twitter-swearing_n_1099126.html">smorgasbord of swearage.</a> "This is a f---ing disgrace... closure again. And on the Budget! There's not a democracy in the world that would tolerate this jackboot s---." And the cherry on top? Telling one of his followers, "F-- you."

• What About Bob?

  Interim Liberal Leader Bob Rae took a page from Pat Martin's profanity playbook on Wednesday -- <a href="http://www.huffingtonpost.ca/2011/12/14/bob-rae-twitter-bs-young-liberals_n_1149155.html?1323898891">and took it to Twitter.</a> A tweet about a feud between liberals Zach Paikin and Max Naylor may have caught him before breakfast. "What bullshit is this?" he tweeted back. Sure, the word likely ceased offending most people decades ago. In fact, we don't even bother covering most of the letters with asterisks. But hey, it does incorporate the s-word - which we still cover with asterisks.

• No Fuddle Duddling Around

  Unlike his father, Justin Trudeau didn't merely mouth the words. In fact, he let them ring out from the rafters at the House of Commons on December 14. 'You piece of sh---' The recipient? Environment Minister Peter Kent. You know, Canada's <a href="http://www.huffingtonpost.ca/elizabeth-may/canada-kyoto-protocol-withdrawal_b_1145648.html">public face of Kyoto withdrawal.</a> Also unlike his father, young Trudeau probably knew the Fuddle Duddle Defence wouldn't cut it. So within minutes of uttering the words, he owned up to them. "I lost my temper and used language that was most decidedly unparliamentary and for that I unreservedly apologize and withdraw my remark," Trudeau said at the end of question period.

• 15-Year-Old 'Jack Ass'

  <a href="http://www.huffingtonpost.ca/2012/01/10/tony-clement-jackass-twitter_n_1196261.html">Treasury Board President Tony Clement was forced to apologize after calling 15-year-old Keith Pettinger a "Jack ass"</a> in a private Twitter message. Clement sent the message after the teen criticized the spelling in one of the minister's tweets.