Foreign Affairs Minister Peter MacKay is in hot water after he allegedly referred to his former romantic interest Belinda Stronach as a dog -- a remark he has denied making.

His comment came during a heated exchange in the House of Commons over the government's new Clean Air Act.

While the government was being peppered with questions about the new Clean Air Plan, Liberal MP Mark Holland says a Liberal jokingly asked MacKay about the impact of pollution on humans and animals: "What about your dog?''

According to Holland, MacKay motioned toward Stronach's empty seat and replied: "You already have her.''

"Mr. Speaker, this is clearly shameful and the minister owes an apology to this House," said Liberal MP Mark Holland. "It is a shameful display that he absolutely must apologize for."

Liberal MP David McGuinty said the remark was loud and unmistakable.

"At least 10 members of our caucus heard it loud and clear and it would be very very difficult for the minister of foreign affairs to deny what he said,'' McGuinty said.

In Halifax on Thursday night for a speech to a Tory fund-raiser, MacKay denied saying anything derogatory about Stronach and suggested that his critics consult Hansard.

"I made no dog comment,'' MacKay told reporters, and blamed the fuss on Liberal partisan politics.

"It's what it's all about. It's a distraction away from their own inadequacies.''

Dan Dugas, a spokesperson for MacKay, argued the insult may have never happened because it wasn't transcribed.

"I've checked the official record of House proceedings and there is no such comment," he told The Canadian Press.

But such transcripts usually omit or skip any comments during heckling.

Stronach was meeting with child-poverty groups in Montreal and was not in the House at the time, Liberal officials said.

She learned about the alleged incident during her drive back to Ottawa, when she received hone calls from colleagues.

She issued a brief statement late Thursday: "I am really disappointed that Peter MacKay would say something like that.''

It wouldn't be the first time that the foreign minister compared his ex-girlfriend to a canine.

Shortly after Stronach left the Conservative party in May 2005, MacKay retreated to Nova Scotia to "clear his head" as he explained then.

The Globe showed a picture of the minister looking thoughtful as he posed on his property with a dog.

But that dog was later revealed to belong to a neighbour, not MacKay.

A recent book by National Post columnist Don Martin described MacKay's "volcanic fury" when Stronach revealed her plans to leave the Tories.

"Belinda: the Political and Private Life of Belinda Stronach" also suggests his fiery reaction was enough to make Stronach reconsider her decision.

"Maybe I was naïve in some ways," Stronach told Martin. "I still think it's possible to see someone in an opposite party.

Clearly he didn't agree. I would've liked another day to talk him through it."

Since that high-profile relationship breakdown, Stronach recently became entangled in former Maple Leaf Tie Domi's divorce proceedings.

Both Stronach and Domi were seen attending a charity event together during the Toronto International Film Festival, and Domi's wife Leanne later mentioned Stronach as a potential cause for her marital troubles.

In a Sept. 18 divorce application, Leanne Domi said her marriage was doomed because of an "intimate, sexual relationship'' between Stronach and her husband.

Stronach denied the charge, issuing a statement that "any problems between Tie and Leanne Domi are not related to me."

With files from The Canadian Press