A 69-year-old Conservative MP is accusing a Liberal MP of "elder abuse," racism and sexism for what she calls intimidation during an incident aboard a parliamentary bus.

Conservative MP Alice Wong said Liberal MP Adam Vaughan stood over her, pointed and displayed an "awful" attitude on Wednesday aboard a bus after Question Period in the House of Commons.

"When I got off the bus, I said, 'This is a form of senior abuse – elder abuse.' It's verbal," Ms. Wong, who represents the Vancouver-area riding of Richmond Centre, said on Thursday.

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"You're looking at three things right now. One is racism: I'm Asian. One is ageism: I'm a senior. And the other way is sexism: I'm a woman."

Speaking before Ms. Wong talked to reporters, Mr. Vaughan, parliamentary secretary to the Minister of Families, said he disputes the description of the interaction, but said it doesn't matter how he feels about it. "The issue is how she felt. She feels she was intimidated," he said. His office did not respond to a follow-up request made after Ms. Wong's accusations.

"No member of Parliament should ever feel that way, and I regret the exchange, however civil I thought it was, left her feeling that way," Mr. Vaughan said on Thursday, outside of a committee meeting both he and Ms. Wong were attending. He apologized in the Commons on Thursday night, but Ms. Wong was not present to hear it, and will return on Monday.

The incident happened as MPs were aboard a bus outside Parliament Hill. Ms. Wong said she was seated at the front of the bus when Mr. Vaughan got on. She said he was upset with some comments she had made during Question Period about the Liberal government's participation in the Beijing-based Asian Infrastructure Investment Bank. Ms. Wong, who has questions about the bank, said she emotionally shouted out that "Canada is our home" during the proceedings, and Mr. Vaughan approached her on the bus about it.

"He's a tall guy and he's pointing at me … commenting, 'Why are you against international investment?'" Ms. Wong said. "Intimidating me in that bus, I don't think that's the proper way, behaviour, as a member of Parliament."

Ms. Wong raised the bus incident in the Commons on Thursday as a point of order, calling it a "grave and disturbing matter," and asked Speaker Geoff Regan to make a ruling over parliamentary privilege.

She said she has not decided on what steps to take next, but will now ask a young staff member to accompany her aboard the bus.

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Mr. Vaughan, however, described the bus incident differently.

He said he simply stopped to tell Ms. Wong about the "significant opportunities" the infrastructure bank would create for architectural, engineering and infrastructure firms in his Toronto riding, before moving on to the back of the bus and taking his seat. He added that the bus full of mostly Conservative MPs told him which issues to focus on.

When asked if he raised his voice, Mr. Vaughan said: "I don't believe I did. I didn't.

"But the issue is not what I felt I did or what I thought I did. The issue is how she felt. She feels she was intimidated. That's not a position anybody in the House of Commons should find themselves in," he said.

Ms. Wong's account of the incident is backed up by Conservative MP Shannon Stubbs, who was sitting behind her on the bus. Ms. Stubbs told The Globe and Mail that Mr. Vaughan was patronizing and rude.

"He was berating her. His voice was loud, he was pointing down at her, waving his hands," Ms. Stubbs said. "I just can't even believe that unbelievable hypocrisy coming from Liberals who are, like, apparently the biggest and best feminists … and here's this guy berating this elderly lady on a subject that she knows about."

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Liberal MP Mary Ng, who was seated beside Ms. Wong, said she couldn't hear exactly what was said. "Adam spoke a few words to Alice, and then he went to the back of the bus. So, that's what happened," Ms. Ng said.

When asked if she understood why Ms. Wong may have felt intimidated, Ms. Ng said, "I don't want to interpret another colleague."

Ms. Wong said the incident reminded her of an event that happened when she came to Canada from Hong Kong 38 years ago. She was driving in Vancouver when she was stopped by police for speeding and told by a police officer to "talk to your big brother."

"Right now, the same thing should not happen. I think women, especially women of multicultural background should stand up. And there's no way we should tolerate it."