MONTREAL - Opposition MPs are calling for a Conservative cabinet minister to resign over a brewing contract controversy on Parliament Hill.

In the House of Commons on Monday, the Liberals, New Democrats and Bloc Quebecois all demanded Natural Resources Minister Christian Paradis step down from his post.

Paradis was the guest of honour at a Conservative party fundraiser in the Montreal-area riding of Bourassa in January 2009.

Montreal businessman Paul Sauve threw the fundraiser months after his company got a $9-million contract to renovate Parliament Hill's West Block.

Paradis was public works minister at the time of the fundraiser, but not when Sauve got the contract.

Sauve says he paid Tory-connected businessman Gilles Varin to help get the job. The company went bankrupt a year later and lost the contract.

The RCMP are now investigating the West Block project.

Sauve says Varin and Gilles Prud'Homme, head of a Montreal-area Conservative riding association, both encouraged him to throw a political fundraiser months after winning the West Block deal.

Paradis initially maintained he did not discuss any government business at the fundraiser.

"At no time was there any discussion about government business," he told the Commons earlier this month. "It was strictly a fundraising event."

He later changed his story and said he congratulated Sauve for winning the West Block deal.

Then Paradis conceded he listened to another construction boss gripe about the federal contracting process.

That had MPs calling on Paradis to resign.

"How can Canadians believe this minister after he has changed his story three times?" Liberal MP Marcel Proulx asked.

"What will it take? How many other versions will the minister have to go through before they put him out of his misery and fire him?"

Paradis denied any wrongdoing. Current Public Works Minister Rona Ambrose and Conservative House Leader John Baird rose to the embattled minister's defence.

"The minister acted entirely appropriately," Baird said.

"When an individual approached him and notified him of the fact that he had been awarded a government contract, he congratulated him. When an individual came forward and made an inquiry about an upcoming contract, he did the right thing and referred them to a non-partisan public servant."

Bloc Quebecois Leader Gilles Duceppe says he's not buying the government's explanation.

"Not at all, not at all," he said. "I mean we will make sure that those people will have to testify in committees, especially him, since in the past he was saying he was responsible for all his employees. So now we are asking him to be responsible for himself."

Meanwhile, the Conservatives distanced themselves from fresh allegations surrounding the West Block contract.

Masonry work on the renovation ground to a halt Friday after subcontractor RJW Stonemasons walked off the job and went to the RCMP.

Company president Bobby Watt says he isn't being paid by the Montreal-based bonding company running the project. He claims he's being squeezed out of the masonry job in favour of another firm and he's asked the RCMP to look into that.

Ambrose says the matter is between the companies and the government is not involved.

"The government of Canada has no contractual relationship with the company that is mentioned," she said. "This is a dispute between two private entities."