Opposition MPs are calling on Prime Minister Stephen Harper to apologize after at least three Conservative MPs made crude arm gestures across the floor of the House of Commons.

"It was regrettable last night all of us in the House witnessed a member of the Conservative caucus acting in a totally unacceptable matter," Interim Liberal Leader Bill Graham said during question period on Wednesday.

"We raise the matter today because these actions were not only insulting to Parliament, it showed contempt and disrespect for all Canadians."

Oshawa MP Colin Carrie; Jacques Gourde, parliamentary secretary to Agriculture Minister Chuck Strahl; and Pierre Poilievre, parliamentary secretary to Treasury Board President John Baird, acted out the crude motion as MPs voted on a farm bill Tuesday evening -- with the latter two members caught making the gestures on the House of Commons camera.

"It's outrageous. It's a disgrace for the institution. We have to be respectful of the institution," Quebec Liberal MP Denis Coderre said Wednesday.

"I'm against that kind of thing," added Manitoba New Democrat MP Pat Martin. "I carry a picture of my mother in my pocket so I want thing to be at a high standard of decorum in the House of Commons."

Conservative Parliamentary Secretary Jason Kenney conceded that parliamentarians get carried away from time to time.

"It's appropriate when they do so, to apologize," said the Calgary-area MP.

"But I find it strange that there is nothing else for the Leader of the Opposition to ask questions about, when the member has already apologized," Kenney said.

Several MPs also alleged that they saw Poilievre standing behind the curtains in the House of Commons mocking Speaker Peter Milliken.

He was "mocking you, Mr. Speaker, and with you the dignities of the members of this House and every Canadian citizen that sent us here to respect our democracy, Mr. Speaker," said Graham.

Poilievre and Gourde expressed regret Wednesday for the gestures.

But Gourde said he believes the House "misinterpreted" his gesture. "If the individuals misinterpreted my hand gesture, I would apologize for that, I would apologize to the house," he said.

Poilievre said, meanwhile: "I wish to say that as I am a gentleman of this house, that if any of my gestures have offended them or any member in this house, I wish to apologize and withdraw them."

Liberal MP Marlene Jennings charged that this apology did not go far enough.

"He said the members misinterpreted his gesture and he said 'If I offended someone, I apologize.' That's not a real apology," said the Montreal-area MP.

"The prime minister should answer for him in the House today. He should say he doesn't accept this type of behaviour and he should dismiss him immediately."

But Kenney called Jennings' charges "ridiculous," accusing the Liberals of trying to distract the government from the important issues at hand.

The opposition, particularly the Bloc Quebecois, had been heckling the government during the vote when the MPs made the gesture.

The gesticulation -- suggesting an anatomically impossible act -- involves crossing both arms at the elbow, with one moving in an upward direction.