BURNABY, B.C. – Federal NDP Leader Jagmeet Singh says a public inquiry is necessary in the scandal involving engineering giant SNC-Lavalin and Canada's former justice minister.

Singh says serious questions need to be answered about the scandal that cuts to the heart of Canada's democracy.

Vancouver member of Parliament Jody Wilson-Raybould resigned from cabinet last week, days after a report that says she was pressured to help SNC-Lavalin avoid criminal prosecution when she was justice minister.

She was moved to veterans affairs in a cabinet shuffle last month before she resigned, saying she was getting legal advice on what she was permitted to say about the claims.

Singh, who's campaigning in Burnaby, B.C., for a byelection next Monday, says Prime Minister Justin Trudeau's Liberal government appears to be acting on behalf of its "friends" in this situation.

He says after Liberal justice committee members attempted last week to obstruct any attempt to get to the bottom of the allegations, while the prime minister repeatedly changed his story, it's become clear that a public inquiry is needed.

The New Democrats will is also asking Trudeau to allow Wilson-Raybould to be able to speak about the issue.

The party will ask for a vote on both measures later this week, he says.

"These are things that Canadians demand," Singh says.

The call comes as Gerald Butts, Trudeau's principal secretary and longtime friend, resigned.

In a statement, Butts denies the accusation that he or anyone else in the office improperly pressured Wilson-Raybould to help SNC-Lavalin avoid a criminal case on corruption and bribery charges related to government contracts in Libya.