In a nutshell
Mr Trudeau has been accused of pressuring his former attorney general to cut a deal with a company facing corruption charges – and retaliating when she refused to play ball.
The revelations could cost Trudeau the October general election, some pundits say.
The former AG, Jody Wilson-Raybould, says Trudeau and his staff spent months trying to convince her that taking the company to trial would cost Canadians jobs, and their party votes.
She also says she was subject to "veiled threats", which she believes were made good when she was shuffled out of her department.
Now another minister, Jane Philpott, has quit saying it was "untenable" for her to continue due to "serious concerns" raised by the case.