Two former ministers in Justin Trudeau’s administration will run as independent candidates in this year’s federal election, reopening wounds from a recent political scandal that has damaged the prime minister’s popularity and cast doubt on the Liberal party’s ability to form a government in October.

In separate events held on either side of Canada on Monday, former ministers Jane Philpott and Jody Wilson-Raybould announced they would hold no party affiliation as they run for parliament.

In February, Trudeau’s office was accused of interfering in the prosecution of the engineering giant SNC Lavalin. Trudeau denied the allegation, saying there was no wrongdoing in the case.

Philpott and Wilson-Raybould publicly rebuked Trudeau, and in April they were expelled from the Liberal party.

“It’s for those young girls I want to say there is a future; don’t ever be afraid to speak the truth,” Philpott said of her decision to stay in politics. “What lesson would it be for those young girls if I walked away?”

Philpott and Wilson-Raybould were rising stars in the Liberal party and held top ministerial positions. Wilson-Raybould was attorney general and later minister of veterans affairs; Philpott started as minister of health and was later moved to minister of indigenous services. She was president of the Treasury Board when she resigned.

At their separate events, the two spoke of the importance of maintaining independent voices in government, and acknowledged they had remained in close contact while choosing their new political paths. The former ministers also spoke about the need for bold action on fighting climate change as a top priority; both had previously been rumoured to be considering joining the Green party.

Their decision to run as independents could damage the Liberal party once campaigning begins, with Liberals worried the two could inadvertently help the Conservatives form a government in October.

At at her announcement in Markham, Ontario, Philpott did not criticise the prime minister directly.

The election of independent members of parliament in Canada is rare – the last one in Philpott’s constituency of Markham-Stouffville, Ontario, was in 1984. But Wilson-Raybould and Philpott remain popular among their constituents.

“She’s got a moral compass. She acted from principle,” said Steve Borlak, a voter in Markham-Stouffville. “It’s so refreshing … The idea of a politician having a moral compass and doing the right thing. It’s stunning.”