The head of Canada's third party has claimed that too often, Justin Trudeau favours the interests of rich Canadians over regular Canadians.

NDP Leader Jagmeet Singh made the comment in Burnaby today as he demanded a public inquiry into what his party is calling the "Liberal corporate prosecution scandal".

It's in reference to allegations that staff in the prime minister's office pressured former justice minister Jody Wilson-Raybould to encourage prosecutors to drop charges against Montreal-based SNC-Lavalin.

The construction-services giant has been seeking a remediation agreement, which became possible when the Trudeau government inserted this type of deal in an omnibus budget bill.

SNC-Lavalin faces bribery and corruption charges in connection with its dealings with the government of former Libyan dictator Moammar Ghadafi.

"The Liberals have been shutting down attempts to get to the truth, or even hear from those involved, and Mr. Trudeau's story changes every day," Singh said. "So today, we're calling for an independent public inquiry into this corporate prosecution scandal—because Canadians deserve to know if their government is working for them or for a massive corporation with deep ties to the Liberal party."

The prime minister's personal secretary, Gerald Butts, resigned today while defiantly denying that he or any other staff exerted pressure on Wilson-Raybould.

Meanwhile, NDP justice critic Murray Rankin plans to table a motion in Parliament calling for an indpendent inquiry led by a former judge. The motion will also urge Trudeau to waive solicitor-client privilege, which has prevented Wilson-Raybould from speaking about this issue.