Fending off new opposition calls to resign following senior civil servant Sue Gray's report, he vowed administrative changes to his Downing Street operation.

"I'm sorry for the things that we simply didn't get right, and also sorry for the way this matter has been handled," Johnson said.

"I get it, and I will fix it," he said.

"Yes, we can be trusted to deliver," Johnson added, stressing his post-Brexit agenda and action against Russia over its threats to Ukraine.

"I am going to get on with the job."

Gray admitted her 12-page report was limited in scope after London's Metropolitan police force launched its own investigation into 12 parties held in Downing Street over the past two years.

While Johnson said all sides should await the Met's own findings, opposition Labour leader Keir Starmer said the police involvement was "a mark of shame".

"He is a man without shame," Starmer said, urging Johnson's Conservative cabinet allies to depose him instead of "supporting further misconduct, cover-up, and deceit".