The PM allegedly pressured former justice minister and attorney general Jody Wilson-Raybould to curtail the criminal prosecution of a multi-million-dollar corruption and fraud case against SNC-Lavalin, redirecting the matter out of the courts and into a "remediation agreement", which would have spared the company the negative financial and reputational consequences of a criminal trial - the most devastating of which would include a 10-year ban from accepting government contracts, a stipulation which would economically cripple the Montreal engineering firm.
In the meantime, he said Wilson-Raybould "confirmed for me a conversation we had this fall where I told her directly that any decisions on matters involving the director of public prosecutions were hers alone".
If then-attorney general Jody Wilson-Raybould was informing the prime minister about her policy on the issue, or discussing options, that's fair game apparently.
Wilson-Raybould had been Canada's first Indigenous justice minister and the face of Trudeau's commitment to make reconciliation his top priority.
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Trudeau also said he had "full confidence" in Wilson-Raybould and suggested she would have resigned from cabinet on principle if she had felt anyone had tried to improperly pressure her.
The now-former veterans affairs minister announced her decision in a letter Tuesday addressed to Prime Minister Justin Trudeau.
For the details of Trudeau's involvement in tampering with the SNC-Lavalin case, however, all Scheer has to go on is an anonymously-sourced report in the Globe and Mail.
Wilson-Raybould's letter does not say exactly why she's quitting.
"The longer he refuses to do this, the more guilty he appears to Canadians". "I only wish that I could have served you longer", she writes.
Both Scheer and NDP Leader Jagmeet Singh called on the Liberals to support an opposition motion to have the House of Commons justice committee investigate the allegation that Wilson-Raybould was pressured.
Meanwhile, at the request of two NDP members, the federal ethics commissioner has launched an investigation into the matter.
"Justin Trudeau promised Canadians he would change the way politics worked in Ottawa, but instead his Liberal government continues to prioritize helping insiders and the rich get ahead".
The Tories and New Democrats want nine high-ranking officials - including members of Trudeau's inner circle and the new justice minister, David Lametti - to testify before the committee.
Garrison Settee, grand chief of the Manitoba Keewatinowi Okimakanak Inc., a group representing 30 First Nations in northern Manitoba, echoed that sentiment.