A top Downing Street aide has resigned after sending sexually explicit messages about independent MP Diane Abbott, Sky News understands.

Paul Ovenden, who was the director of strategy at Number 10, is understood to have left the role on Monday after a number of instant messages from 2017 became public.

Sky News understands he did so to avoid becoming a “distraction” for Sir Keir Starmer, just days after he was forced to sack the UK’s ambassador to the US – Peter Mandelson – over his ties to disgraced financier Jeffrey Epstein.

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The messages, exchanged between Mr Ovenden and a female colleague, contained the graphic retelling of a conversation he reportedly overheard about Ms Abbott while at a party.

The former aide has alleged these were not his original words, but said he “deeply regrets” sharing them.

He said: “I really, deeply regret my sharing this story, and the hurt and embarrassment its publication will cause.

“Accordingly, I have brought forward my resignation to today as I do not want to be a distraction from the government’s work.”

It is understood Mr Ovenden announced to colleagues before the summer recess he was leaving his role, and had planned to leave “quietly and quickly” sometime this month.

However, in the wake of the publication of these messages, Mr Ovenden “brought forward” his resignation to today.

The messages, exchanged with a female colleague and seen by Sky News, described a game of “shag, marry, kill” the aide overheard while at a party in May 2017.

This involved explicit descriptions about suspended Labour MP Ms Abbott.

A Number 10 spokesperson said: “These messages are appalling and unacceptable.

“As the first black woman to be elected to parliament, Diane Abbott is a trailblazer who has faced horrendous abuse throughout her political career.

“These kinds of comments have no place in our politics.”

Sky News has contacted Ms Abbott for comment.

The latest Number 10 resignation comes as Sir Keir admitted he never would have appointed Lord Mandelson to the post of UK ambassador to the US if he had known what he knows now about the extent of his association with Epstein.

Speaking publicly for the first time since he sacked Mandelson last Thursday, the prime minister explained that a “due diligence process” was conducted before he was appointed to the post in February.

“I knew of his association with Epstein,” Sir Keir said.

“But had I known then what I know now, I’d have never appointed him.”

Just days before Lord Mandelson was sacked, Angela Rayner resigned as deputy prime minister and housing secretary after admitting she did not pay enough tax on her second home.

She also quit as deputy leader of the Labour Party, an elected post.

Sir Keir’s second-in-command admitted to Sky News political editor Beth Rigby on the Electoral Dysfunction podcast that she should have paid the higher rate of stamp duty on a home she bought in Hove, East Sussex, as it was her second property.