Prime Minister Justin Trudeau said "sexual harassment is a systemic problem" and "when women speak up, we have a responsibility to listen to them and to believe them," in brief remarks on Sunday.

He spoke to reporters at the opening of a meeting of Liberal MPs in Ottawa ahead of the resumption of Parliament on Monday. Trudeau also spoke about the economy and ongoing trade negotiations, but the scourge of sexual harassment in politics will still dominate discussion after last week's high profile resignations, including Ontario Progressive Conservative leader Patrick Brown and Kent Hehr, one of Trudeau's own cabinet ministers.

'It's a dam breaking,' says the NDP's House Leader Ruth-Ellen Brosseau. 10:36

"We will always defend women," Trudeau said. "As I said last week in Davos — #MeToo, Time's Up, the Women's March are not discrete campaigns for social change. It is a movement, and a movement whose time has come."

Hehr, formerly the minister for sport and disabilities, resigned from the federal cabinet on Friday after a woman came forward to allege that he had made inappropriate comments to her when he was an MLA in Alberta.

In announcing Hehr's resignation from office, the prime minister said there would be an investigation into the allegation against him. But, in the meantime, Hehr will remain a member of the Liberal caucus.

A second woman subsequently told CBC News that she had been "groped" by Hehr, while others said they had been warned about Hehr's behaviour toward women.

Liberal Government Whip Pablo Rodriguez said on Sunday that the allegation in the CBC report has also been forwarded to investigators.

The MP for Calgary Centre was not present for Sunday's caucus meeting, but his former cabinet colleagues faced questions about his status with the party and the allegations against him as they arrived on Sunday morning.

"I think it's really important that we allow the due process to take place. I think the fact that he stepped away from his cabinet position is the right thing to have done," said Karina Gould, minister for democratic institutions. "Sexual harassment on the Hill is a very serious issue and we need to take it seriously. But we also need to make sure that we're allowing due diligence and due process."

When the House of Commons resumes sitting on Monday, MPs are scheduled to first debate Bill C-65, which would establish new rules for dealing with sexual harassment in federally regulated workplaces, including Parliament Hill.