She also says that she has retained former Supreme Court justice Thomas Cromwell to advise her on this front.
Wilson-Raybould, however, has chosen not to speak publicly on the allegations, saying she is protected by client privilege and cabinet confidentiality.
Wilson-Raybould - who has kept largely silent since a news report claimed the Prime Minister's Office pressured her to help Quebec-based engineering firm SNC-Lavalin avoid criminal prosecution - announced she was quitting the Liberal cabinet this morning.
I look forward to continuing to serve as the Member of Parliament for Vancouver-Granville.
The letter, from the Union of B.C. Indian Chiefs' executive, says the recent statements by reported Liberal party insiders are "cowardly, low blows aimed at discrediting the staunch work ethic Minister Wilson-Raybould has maintained".
Jody Wilson-Raybould and Justin Trudeau in happier times.
"If Justin Trudeau and the Liberal government shut the justice committee's work down, it would send a risky signal to Canadians about the state of our democracy", Singh said in a statement.
But in a letter to the prime minister announcing her resignation on Tuesday, Ms Wilson-Raybould said that she is "aware that many Canadians wish for me to speak on matters that have been in the media over the last week".
Wilson-Raybould, who was demoted to the veterans-affairs portfolio in a January cabinet shuffle, was a no-show at Trudeau's events in the Vancouver area, which were attended by a number of other British Columbia Liberal MPs.
SNC-Lavalin faces charges of fraud and corruption in connection with almost $48 million in payments made to Libyan government officials between 2001 and 2011.
Trudeau is scheduled to be in Winnipeg later today where he will face questions about Wilson-Raybould's resignation.
Trudeau's comments came shortly after federal ethics commissioner Mario Dion confirmed he has launched an investigation into the allegation the PMO improperly tried to help SNC-Lavalin avoid criminal prosecution.
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.
Shortly before her resignation announcement, the Union of British Columbia Indian Chiefs issued an open letter to Trudeau demanding that he publicly condemn "the racist and sexist innuendo" that's circulated about Wilson-Raybould since her demotion, suggesting that she's hard to work with and not a team player. "And at the end of the day, I abide by the long-standing principle that when acting as attorney general, I will apply my judicial mind to a decision, and not my political mind".