4 of Boris Johnson's key aides quit, marking latest blow for the U.K. PM

Four top aides to Boris Johnson resigned Thursday, marking the latest setback for the British prime minister whose government has been embroiled in scandal in recent days.

Johnson's head of policy, Munira Mirza, chief of staff Dan Rosenfield, principal private secretary Martin Reynolds, and communications director Jack Doyle all left their posts Thursday, just days after a damning investigation revealed that multiple parties took place at Downing Street while the rest of the United Kingdom was living under strict COVID-19 lockdown rules.

The report, released Monday, uncovered multiple parties and a culture of excessive drinking at Downing Street. The report's author, senior civil servant Sue Gray, said there had been a "failure of leadership" in Johnson's government.

"Against the backdrop of the pandemic, when the Government was asking citizens to accept far-reaching restrictions on their lives, some of the behavior surrounding these gatherings is difficult to justify," the report said.

Mirza's departure is the most consequential. She was one of Johnson's longtime allies and a key political player who helped shape the prime minister's platform -- some of which made her unpopular with other members of his ruling Conservative party.