OTTAWA -- Prime Minister Justin Trudeau's former principal secretary, Gerald Butts, wants to give his side of the story in the SNC-Lavalin affair.

Butts wrote the House of Commons justice committee Thursday, requesting he be called as a witness.

His request came one day after former attorney general Jody Wilson-Raybould testified that she faced relentless pressure -- and even veiled threats -- from Trudeau, senior prime-ministerial aides, Canada's top public servant and the finance minister's office to interfere in the criminal prosecution of SNC-Lavalin. Butts was among those she accused of inappropriate pressure tactics.

Butts said he believes he has evidence that will help the committee get to the bottom the affair. He added that he will need a short time to receive legal advice and compile relevant documents before testifying.

Trudeau's longtime friend and most trusted adviser resigned as his principal secretary last week amid the mushrooming controversy over the government's attempts to help SNC-Lavalin avoid a criminal trial on charges of bribery and corruption related to its bid to secure contracts in Libya.

In a statement announcing his resignation, Butts categorically denied that he or anyone else in Trudeau's office pressured Wilson-Raybould. He said he was quitting to avoid distracting from the government's agenda and suggested he wanted to be free to defend himself.

"My reputation is my responsibility and that is for me to defend," he said in the statement.

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On Wednesday, Wilson-Raybould specifically accused Butts and Trudeau's chief of staff, Katie Telford, of pushing for an external legal opinion on the option of negotiating a remediation agreement with SNC-Lavalin -- a kind of plea bargain that would force the company to pay restitution but avoid the potentially crippling impact of a criminal conviction. In a Dec. 18 meeting, Wilson-Raybould said Butts told her chief of staff, Jessica Prince, that there was "no solution here that does not involve some interference."

Earlier Thursday at an event in Montreal, Trudeau said it will be up to the federal ethics commissioner to decide who is telling the truth in the SNC-Lavalin affair -- Trudeau or Wilson-Raybould.

But Conservative Leader Andrew Scheer argued that it's time for the RCMP to investigate what he contends is possible obstruction of justice by the prime minister.

Scheer wrote RCMP Commissioner Brenda Lucki on Thursday, calling for an investigation. He also reiterated his call for Trudeau to resign.

Trudeau said he totally disagrees with how Wilson-Raybould characterized discussions she had with him and others about the case. And he said ethics commissioner Mario Dion can be trusted to settle disagreements over what happened. Dion initiated an investigation into the affair two weeks ago.

"Canadians need to know that we have an officer of Parliament who is tasked with a specific role to make sure that in questions where there are disagreements amongst politicians, amongst elected officials, there is an arbiter who is empowered to be like a judge, who is an officer of Parliament, who will make a determination in this issue," Trudeau said after an announcement at the Canadian Space Agency.

Over nearly four hours of explosive testimony Wednesday, Wilson-Raybould told the House of Commons justice committee there were 10 meetings and 10 phone calls involving 11 people between September and December 2018, all aimed at getting her to "politically interfere in the exercise of prosecutorial discretion in my role as the attorney general of Canada."

Wilson-Raybould detailed a September meeting she said she had with Trudeau where he brought up the possibility of SNC-Lavalin leaving Quebec and the spectre of job losses during a provincial election campaign. Trudeau did not deny there were "many and broad conversations about the importance of defending jobs" across the country but he insisted those discussions did not cross any legal lines.

"Canadians expect their government to look for ways to protect jobs, to grow the economy, and that's exactly what we've done every step of the way," Trudeau said. "We've also done it in a way that has respected our laws, and respected the independence of the judiciary -- of that there actually is no doubt. There are disagreements in perspective on this, but I can reassure Canadians that we were doing our job and were doing it in a way that respects and defends our institutions."

Top ministers echoed the prime minister in separate appearances Thursday.

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In Toronto, Finance Minister Bill Morneau denied that his chief of staff, Ben Chin, did anything inappropriate in discussing the SNC-Lavalin case with Wilson-Raybould's staff.

"My staff, of course, is going to be constantly in communication with other teams across the government, always talking about the importance of the economy, always talking about the importance of jobs and that is their appropriate role," Morneau said. "I think that Ben was acting entirely appropriately in that capacity."

Morneau did not directly address Wilson-Raybould's assertion that Chin pressured her staff to take into consideration the political impact on last fall's Quebec election if SNC-Lavalin were to move its operations out of the country. He did say that he did not direct Chin to do that.

Morneau emphasized that the company employs 9,000 people across the country and thousands of pensioners depend on its continued operation. It was appropriate to take that into consideration, while respecting the rule of law, he said.

In a speech to the Empire Club of Canada, Wilson-Raybould's successor as justice minister and attorney general, David Lametti, said her testimony was an extraordinary symbol of transparency in the government. He also said it's useful for the attorney general to sit at the cabinet table -- unlike in some other jurisdictions, where the attorney general and justice minister are distinct.

"Just like the world outside politics, each of us is made stronger by talking to each other and coming to better understandings together," he said. "I believe that these discussions can improve the quality of decision making. The attorney-general is not an island, even in circumstances where a final decision rests with him or her."

While Trudeau and his ministers seemed intent on projecting a business-as-usual confidence, the Conservatives requested an emergency debate in the House of Commons, scheduled for Thursday night, on Wilson-Raybould's testimony. The NDP supported the request, which was granted by Speaker Geoff Regan.

Wilson-Raybould was shuffled to the veterans-affairs portfolio in January, a move she believes was a result of her not caving into the pressure on SNC-Lavalin.

As for Wilson-Raybould's future as a Liberal, Trudeau said he is still mulling over whether she will be allowed to remain in caucus or run for the party in this fall's federal election.

"I have taken knowledge of her testimony and there are still reflections to have on next steps," he said.