Van Loan acknowledged Thursday he used an inappropriate word during the confrontation.
However, New Democrats weren't satisfied, questioning how Van Loan can remain government House leader after displaying so little regard for proper conduct.
The incident erupted Wednesday after the NDP unsuccessfully attempted to invalidate a vote on the government's omnibus budget bill due to a procedural snafu.
Microphones were shut off during the incident, but video tape shows Van Loan stormed across the centre aisle of the Commons, waving his finger at his NDP counterpart, Nathan Cullen, and speaking in a heated manner.
Mulcair, Cullen's seat mate, stood up, whereupon a number of New Democrats surrounded Van Loan and appeared to urge him to leave.
Finally, Defence Minister Peter MacKay rushed over and ushered Van Loan back across the aisle to the government benches.
New Democrats say Van Loan provoked the contretemps, repeatedly dropping the "F-bomb" as he wagged his finger in Cullen's face. They say Mulcair came to Cullen's defence, warning Van Loan to stop threatening his House leader.
Not surprisingly, the Conservatives tell a different story.
Van Loan initially said he merely crossed the floor to talk to Cullen about "the hypocrisy of his complaint" about the budget vote, since the procedural foul-up was the result of a mistake by a New Democrat, deputy Speaker Joe Comartin.
"I was surprised, however, how Mr. Mulcair snapped and lost his temper," Van Loan said in a statement Thursday night.
Conservative MPs also said Mulcair swore at Van Loan.
On Thursday, Van Loan acknowledged using "an inappropriate word" during the contretemps.
"I should not have done that and I apologize for that," he told the Commons. "I would expect the leader of the opposition to do the same."
Cullen offered no apology but said he'd get back to the Commons with an official response from the NDP after speaking privately with the Speaker, Andrew Scheer.
Scheer, who stood by without intervening during the dust-up Thursday, reserved the right to address the matter later.
NDP foreign affairs critic Paul Dewar, one of the MPs who rushed in to urge Van Loan to back off, said Mulcair's response to the unprovoked verbal barrage was "totally appropriate." He said Van Loan is the only one who needs to apologize and maybe even take a "time out."
"I saw (Van Loan) coming across, I could see in his face that he was very upset and in a very aggressive kind of mode and so I've seen that before, in men, and I know it's the best thing to do is to get people away from each other," Dewar said.
"In terms of his apology, frankly, I think it's unbecoming a minister or a House leader. I'm not sure if I was prime minister I'd still have him as a House leader."
Interim Liberal Leader Bob Rae — who prompted Van Loan's apology by raising a point of order on the "somewhat unusual transaction that took place on the floor of the House" — urged MPs to show a "willingness to engage in public discourse without insulting each other" for the remaining few days of the parliamentary sitting.
Noting that Van Loan's eruption occurred after the Speaker had shot down the NDP's attempt to invalidate the budget vote, Green party Leader Elizabeth May said: "I can only conclude the government House leader is a sore winner. I hope we will never see this sort of thing again."
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