Canada's Foreign Affairs Minister Peter MacKay, pictured September 2006, is facing pressure to step down as the fallout from an insulting remark he allegedly made about his former girlfriend, an opposition parliament member, continues to grow. [AFP]

Ottawa -- Canadian Foreign Minister Peter MacKay is facing pressure to step down as the fallout from an insulting remark he allegedly made about his former girlfriend, an opposition parliament member, continues to grow.

The 40-year-old minister is accused of calling Liberal MP Belinda Stronach, also his former lover, a dog, during a heated exchange on Thursday in the House of Commons over the government's new Clean Air Act.

Although MacKay denied uttering the contentious phrase, at least 10 Liberal MPs said they heard it loud and clear, insisting the remark was unmistakable.

While Stronach has demanded a formal apology from MacKay, two opposition parties have also urged him to apologize or resign, and accused the ruling Conservatives of being sexist and disrespectful to women.

MacKay and Stronach, who were romantically linked while serving as caucus colleagues last year, suffered a highly public split when Stronach left the Conservative party to join the Liberals.

According to several Liberals, Liberal MP David McGuinty asked MacKay during Thursday's debate that how the new green plan would help his dog in Nova Scotia. MacKay is alleged to have responded: "You already have her" as he pointed to Stronach's empty seat.

Stronach raised a point of order in the parliament on Friday, asking MacKay to apologize to her and the house. She described MacKay's alleged comments as "very shameful and very disrespectful, hurtful, insulting to women, women in politics."

Two opposition parties, the Liberal party and the New Democratic Party (NDP), have also stepped in the fray, urging MacKay to apologize or to resign.

Interim Liberal leader Bill Graham on Friday urged Prime Minister Stephen Harper to censure MacKay for his "disgraceful" comments and asked MacKay to apologize.

Graham lamented the Conservative party's record on women's rights and said the latest incident "paints a disturbing picture" of the government's "attitude toward Canadian women."

On Saturday, NDP Leader Jack Layton also joined in the clamor, demanding MacKay to apologize or resign as Canada's foreign minister.

Layton dragged in a comment MacKay made during the federal election in January. Layton said that MacKay should also "apologize to (NDP MP) Alexa McDonough for telling her to get back to her knitting when she was criticizing the Afghanistan mission and raising questions about it."

"His apology should go to all women members of parliament and members of the country because ... it's certainly going to discourage women from seeking public office," Layton said. "And in that, he's done a great disservice."

Liberal MP Sheila Copps, who was called insultingly by a Conservative MP in 1985 as "a baby," said MacKay likely fell into a trap made by the opposition and that he has got nobody to blame but himself.

According to some reports, this is not the first time that the foreign minister compared his ex-girlfriend to a canine. He was so enraged by Stronach's defection in May 2005 that he had to retreat to his hometown in Nova Scotia to "clear his head."

During that time a picture of MacKay looking thoughtful as he posed on his property with a dog went public. And it was later revealed that the dog did not belong to him.

According to an analytical article by Canadian Television, this "dog" event is not the first time civility has broken down in Canada's House of Commons.

Since 1867, MPs have banged on their chairs, mimicked the sound of animals, and even thrown projectiles -- at one point, even firecrackers were thrown across the floor, the article said.

The article listed some of the rude remarks made by political celebrities in history, including former Prime Minister Pierre Trudeau swearing a Conservative MP in 1971, using two words "with the first starting with the letter F and the second word starting with O."