The cabinet of embattled Prime Minister Justin Trudeau has been hit with another high-profile resignation over the SNC-Lavalin controversy.

Jane Philpott quit as president of the Treasury Board, saying she has “lost confidence in how the government has dealt with this matter and in how it has responded to the issues raised”.

In a strongly-worded letter to Trudeau, the Markham-Stouffville MP cited alleged interference in the criminal prosecution of the Quebec engineering company.

“Unfortunately, the evidence of efforts by politicians and/or officials to pressure the former Attorney General to intervene in the criminal case involving SNC-Lavalin, and the evidence as to the content of those efforts have raised serious concerns for me,” Philpott wrote in her letter Monday (March 4).

Philpott was referring to Jody Wilson-Raybould, who resigned as justice minister amid allegations that she was pressured by the Prime Minister’s office to help SNC-Lavalin avoid criminal prosecution for fraud and bribery.

“The solemn principles at stake are the independence and integrity of our justice system,” Philpott wrote. “It is a fundamental doctrine of the rule of law that our Attorney General should not be subjected to political pressure or interference regarding the exercise of her prosecutorial discretion in criminal cases.”

When Wilson-Raybould resigned on February 12 this year, Philpott posted on social media a photo of her and the Vancouver Granville MP, saying, ‘I know you will continue to serve Canadians.’

Philipott said the same thing for herself, telling Trudeau, “Although I must regretfully resign from Cabinet, I will continue to serve Canadians in every other way that I can.”

What she cannot do is to defend the Trudeau government as a member of the cabinet.

“In Canada, the constitutional convention of Cabinet solidarity means, among other things, that ministers are expected to defend all Cabinet decisions,” Philpott wrote. “A minister must always be prepared to defend other ministers publicly, and must speak in support of the government and its policies. Given this convention and the current circumstances, it is untenable for me to continue to serve as a Cabinet minister.”

Philpott said that she needs to abide by her values.

“There can be a cost to acting on one’s principles, but there is a bigger cost to abandoning them,” Philpott said.