British Prime Minister Boris Johnson has indicated his determination to remain in his post despite a wave of resignations of disaffected staff.

Johnson came under fire over a series of parties held in the prime minister's office and elsewhere while strict coronavirus lockdowns were in place.

Last week, a senior Conservative Party official appointed by Johnson resigned over sexual misconduct allegations. Even some party members called Johnson's response to the matter insincere.

On Tuesday, Chancellor of the Exchequer Rishi Sunak and Health Secretary Sajid Javid resigned in a show of protest against Johnson.

Javid said at Parliament on Wednesday, "Treading the tightrope between loyalty and integrity has become impossible in recent months."

Javid said, "At some point we have to conclude that enough is enough. I believe that point is now," and that "the problem starts at the top."

When a Conservative Party member urged Johnson to resign, he said he has a "colossal mandate" from the voters and will "keep going."

More than 20 senior government officials and others have announced their resignation.