Canadian PM Justin Trudeau is facing a new challenge after he was set a deadline by some Liberal MPs to decide whether to remain as leader or face some unspecified consequences in the next few days.

For weeks, anti-Trudeau MPs have been meeting in secret to convince caucus members to band together and push him out of the top job to save the party from electoral ruin, reported CBC.

With Trudeau's popularity declining after nine years in power, some 24 Liberal MPs signed a document calling for his exit.

Sources told CBC MP Patrick Weiler read a letter to Trudeau during the party's caucus meeting on Parliament Hill, laying out the arguments in favour of the prime minister resigning now.

The letter included a demand that Trudeau should decide his future before October 28.

About 20 MPs — none of them cabinet ministers — also stood up in the Liberal caucus meeting today to urge Trudeau to rethink his pledge to stay on as leader into the next election, sources told CBC News.

"I didn't think they would put an ultimatum on the table. That shows they have a great deal of resolve here that was unanticipated," one MP told CBC News.

Sources said Trudeau looked uncomfortable at times as MPs questioned his leadership.

It is still not clear what Liberals are planning to do if Trudeau simply ignores their demands.

The MPs are making the demand at a time when relationship between India and Canada has touched new low points.

Trudeau accused Indian officials of having a role in the killing of Khalistani terrorist, Hardeep Singh Nijjar without producing any proof.

India responded sharply after Canada called the Indian High Commissioner and other diplomats "persons of interest" in the killing of Khalistani terrorist Hardeep Singh Nijjar.