Four top aides desert UK's embattled Johnson

British Prime Minister Boris Johnson suffered four staff defections on Thursday as pressure intensified on the embattled leader over lockdown parties and his loose-lipped style of politics.

One of the departures was linked to an inflammatory remark made by Johnson, attacking opposition Labour leader Keir Starmer over a notorious pedophile.

"Being honest, I wouldn't have said it and I'm glad the prime minister clarified it," finance minister Rishi Sunak said in an extraordinary rebuke of his boss.

Sunak is tipped as a leading contender to replace Johnson, if a brewing Conservative revolt against the prime minister develops further. Downing Street confirmed chief of staff Dan Rosenfield was leaving, just over a year after he took on the role with a brief to professionalize Johnson's chaotic operation.

His resignation comes after a top civil servant, in a long-awaited inquiry, condemned "failures of leadership" in Downing Street over a series of parties in violation of COVID restrictions.

Also going is Johnson's principal private secretary, Martin Reynolds, who sent a now-notorious e-mail in May 2020 urging Downing Street staff to "bring your own booze" to one lockdown gathering.

Johnson "thanked them both for their significant contribution to government and No. 10, including work on the pandemic response and economic recovery," a spokesperson said.

Their departures were confirmed not long after those of two other top advisers – director of communications Jack Doyle and head of policy Munira Mirza.

Doyle was implicated in the "partygate" affair after attending at least one Downing Street event that is under investigation by police.

Johnson's long-term ally Mirza quit after the prime minister tried to link Labour's Starmer to the failure by UK authorities to prosecute pedophile and veteran TV host Jimmy Savile, who died in 2011 aged 84.