WATCH | Showdown between embattled UK PM Boris Johnson and Opposition MP

British Prime Minister Boris Johnson vowed Wednesday to stay in power despite the resignations of two top Cabinet ministers and a slew of more junior officials, who said they could no longer serve under his scandal-tarred leadership.

Johnson told lawmakers Wednesday that “the job of a prime minister in difficult circumstances when you’ve been handed a colossal mandate is to keep going.”

The prime minister's hold on power has been shaken by the resignations Tuesday of Treasury chief Rishi Sunak and Health Secretary Sajid Javid.

They quit saying they could no longer support Johnson because of his handling of ethics scandals including the case of a senior official accused of sexual misconduct.

Johnson quickly replaced the two men, but a string of junior ministers have also stepped down, and Johnson's support inside his Conservative Party is shrinking rapidly.

Last week, Chris Pincher resigned as Conservative deputy chief whip after complaints he groped two men at a private club.

That triggered a series of reports about past allegations levelled against Pincher and questions about what Johnson knew when he tapped Pincher for a senior job enforcing party discipline.

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Johnson's office initially said he wasn't aware of the previous accusations when he promoted Pincher in February.

By Monday, a spokesman said Johnson did know of the allegations — but they were "either resolved or did not progress to a formal complaint."

In response to opposition leader Keir Starmer's questioning on promoting Pincher to party Whip following the allegations, Johnson said in hindsight he should have realised the accused "would not change".

Johnson also said "I greatly regret that he continued in office".

Johnson's opponents in the party hope more Cabinet ministers will follow Sunak and Javid, though for now other top officials — including Foreign Secretary Liz Truss, Defence Secretary Ben Wallace and Home Secretary Priti Patel — are staying put.

Opponents are also trying to force another no-confidence vote over the prime minister.

The existing rules require 12 months between such votes, but the rules are made by a party committee and can be changed.

Elections for that committee's executive are due in the next few weeks.