The scandal that could end Justin Trudeau's time as Canada's Prime Minister

Canadian Prime Minister Justin Trudeau's re-election hopes have taken another major hit with a second cabinet minister resigning on Tuesday over an on-going bribery scandal.

Treasury Secretary Jane Philpott announced her decision to resign, voicing serious concerns over Mr Trudeau's recent actions to shield a major Canadian engineering firm from bribery accusations.

Ms Philpott said in a statement: "It grieves me to leave a portfolio where I was at work to deliver on an important mandate. But I must abide by my core values, my ethical responsibilities and constitutional obligations. There can be a cost to acting on one's principles, but there is a bigger cost to abandoning them."

SNC-Lavalin, based in Trudeau's home province of Quebec, is accused of paying C$48m worth of bribes to the Libyan government, in order to secure major contracts. If found guilty, the company would be barred from bidding on federal Canadian projects for a decade. SNC-Lavalin employs nearly 50,000 people worldwide, with 3,400 in Quebec.

Mr Trudeau has caused a division within his Liberal party by actively lobbying for the firm in question to pay a fine, rather than face criminal prosecution and a ban.

Former Attorney General Jody Wilson-Raybould resigned from her role three weeks ago and has since detailed a series of events during which she was pressured by Mr Trudeau and his team to interfere in the justice system to prevent SNC-Lavalin from receiving any ban.

Mr Trudeau also lost the services of long-time advisor and close friend Gerald Butts, though he is still backing the Prime Minister.

"I categorically deny the accusation that I or anyone else in his office pressured Ms Wilson-Raybould," Butts said in a statement.

The loss of Ms Philpott will add further pressure to the reigning Liberal party which was already reeling after Ms Wilson-Raybould shared her version of events.

A poll released on Monday had nearly 25 percent of Canadians saying it will change the way they vote in the October election.