LONDON — One of U.K. Prime Minister Keir Starmer’s most senior aides resigned Monday after lurid emails he sent in 2017 about a prominent left-wing MP were revealed.

Paul Ovenden, the former director of strategy at No. 10, is a close ally of both the prime minister and his chief of staff, Morgan McSweeney. He exchanged sexually explicit messages with a colleague about former Labour MP Diane Abbott that were revealed on Monday by ITV News.

His resignation comes at a perilous moment for Starmer: Two senior members of his government recently quit after an attempt to reset his premiership.

Ovenden said he had already been planning to resign but had brought it forward to avoid further distractions to Starmer’s leadership.

“I am accused of eight years ago as a junior press officer sharing with a female colleague the details of a silly conversation that I was party to with other female staff members,” he said in a statement to ITV News.

“Before summer, I had announced to some of my colleagues my intention to leave government … I’ve brought forward my resignation to avoid distracting from the vital work this government is doing to positively change people’s lives.”

Starmer is already facing intense scrutiny after revelations concerning the friendship between Ambassador to the U.S. Peter Mandelson and convicted sex offender Jeffrey Epstein led to the sacking of the former.

He also had to accept the resignation of Deputy Prime Minister Angela Rayner two weeks ago, when she was found to have underpaid £40,000 in property tax on her home in Brighton. Her departure forced Starmer to reshuffle his Cabinet.

A No. 10 spokesperson said: “This story involves a former staff member and eight-year-old messages that pre-date employment in government. We don’t comment on staff.”

Ovenden was a key figure in Starmer’s top team, helping the prime minister to make Labour electable again after 14 years in opposition.

“Paul rebuilt a party inherited from Corbyn into a machine capable of a landslide. Advisers will hope that he continues to be leant on by the PM before too long,” said a former colleague of Ovenden.

Emilio Casalicchio contributed to this report.