Conservative Leader Andrew Scheer kicked off the federal election campaign today by accusing Justin Trudeau of lying to Canadians over the SNC-Lavalin scandal and arguing the prime minister has lost the "moral authority" to govern.

The attack meant Trudeau had to defend his role in the affair as he stood at the podium outside Rideau Hall where he officially opened the federal election.

Scheer's accusation was prompted by a story in The Globe and Mail, published late Tuesday evening, that suggested the RCMP were being frustrated in their attempts to interview potential witnesses because their knowledge of the SNC-Lavalin affair was covered by cabinet confidence

The newspaper published another story late Wednesday, quoting former attorney general Jody Wilson-Raybould as saying she was interviewed by the Mounties on Tuesday, a day before the election was called.

Wilson-Raybould told the newspaper that the formal interview took place at the request of the RCMP, but she would not reveal what was said by either party. The former minister did, however, say she had concerns about cabinet confidences shielding witnesses from answering RCMP questions.

CBC news has reached out to Wilson-Raybould and the RCMP, but has not received a response.

Conservative Leader Andrew Scheer said the SNC-Lavalin affairs shows Canadians "just cannot trust Justin Trudeau," while answering questions before the Trudeau called the federal election Wednesday. 0:41

Scheer, who moved up his media availability on Wednesday morning by a few hours to respond to the first report, called on Trudeau to issue a waiver to allow the RCMP to get full answers from witnesses. He rejected a claim that Trudeau had nothing to do with the decision to withhold a waiver.

"We know that the power to waive cabinet confidence and the power to waive privilege rests with the prime minister. That is clear. It's within his power to do so," Scheer said. "He should do it immediately, he should do it today."

A Department of Justice spokesman contradicted that position saying that, in this instance, the Clerk of the Privy Council, the country's top public servant, made the decision to to waive cabinet confidence.

"The government had given the same waiver to the RCMP that was provided to the Conflict of Interest and Ethics Commissioner and the House of Commons standing committee on justice and human rights to permit the same access to cabinet confidences and privileged information," said Ian McLeod.

"The decision to do so was made solely by the Clerk of the Privy Council as guardian of cabinet confidences."

In its first report, the newspaper quoted former RCMP commissioner Bob Paulson, who suggested cabinet confidence is stretched too far.

"In my experience, particularly, cabinet privilege is overasserted and I guess more widely applied than it deserved," he told The Globe.

A Liberal campaign spokesperson said that as of today, the RCMP still has not contacted any current or former PMO staff for documents or interviews related to the SNC Lavalin affair.

Asked during the Rideau Hall news conference about the Globe report, Trudeau offered a short reply.

"We gave out the largest and most expansive waiver of cabinet confidence in Canada's history," he said, referring to the limited waiver he issued to allow Wilson-Raybould to testify before a parliamentary committee.

Liberal Leader Justin Trudeau said he respects the decision the Privy Council Clerk made over the SNC-Lavalin affair during a news conference at Rideau Hall Wednesday. 0:27

Trudeau said the Privy Council Clerk made the decision to cite cabinet confidence in the RCMP examination.

"We respect the decisions made by our professional public servants. We respect the decision made by the clerk," he said.

Last month, Wilson-Raybould, who was at the centre of the SNC-Lavalin affair, told CBC News that she had been contacted by the RCMP in the spring.

She declined to provide any details of that discussion.

Scheer said the latest developments prove Trudeau has not been up-front with Canadians and has lost the moral authority to govern.

Ethics rules violations

"What today shows is that you just cannot trust Justin Trudeau," he said. "He will say anything to cover up his scandals and he'll say anything to get re-elected and Canadians cannot believe the things he says."

Last month, Ethics Commissioner Mario Dion found Trudeau violated the Conflict of Interest Act by trying to influence Wilson-Raybould to overrule a decision denying a deferred prosecution agreement to Quebec-based engineering firm SNC-Lavalin.

In his report, Dion wrote that "the evidence showed there were many ways in which Mr. Trudeau, either directly or through the actions of those under his direction, sought to influence the attorney general."

"The prime minister, directly and through his senior officials, used various means to exert influence over Ms. Wilson‑Raybould. The authority of the prime minister and his office was used to circumvent, undermine and ultimately attempt to discredit the decision of the director of public prosecutions as well as the authority of Ms. Wilson‑Raybould as the Crown's chief law officer," Dion wrote.

SNC-Lavalin is facing bribery and fraud charges related to alleged payments of close to $50 million to public officials in Libya between 2001 and 2011 to secure government contracts. The company is due back in court Sept. 20.