Tim Allan has resigned as Keir Starmer's director of communications.
In a statement on Monday, Allan said he had resigned to allow Starmer to build a "new" team in 10 Downing Street.
His resignation comes just a day after Morgan McSweeney resigned as the PM's chief of staff on Sunday over his role in the decision to appoint Peter Mandelson as US ambassador.
Allan, who was an adviser to Tony Blair in the 1990s, and deputy director of communications at the beginning on Blair's first term as PM, was only appointed No.10 executive director of communications in September last year.
He replaced Steph Driver and Matthew Doyle, who had shared director of comms responsibilities, and was the fourth person to hold the role since Starmer became prime minister in July 2024.
"I have decided to stand down and allow a new No/10 team to be built. I wish the PM and his team every success," he said in a statement.
Starmer is under political pressure over his decision to bring Mandelson into government despite being aware of his links to Jeffrey Epstein.
Last week, the PM said he knew about the former cabinet minister's links to the paedophile financier when he made him the UK's chief representative in Washington, but said that Mandelson lied about the depth and extent of their relationship.
The admission triggered widespread outrage in the parliamentary Labour Party and renewed leadership speculation.
Addressing No.10 staff this morning, Starmer made clear that he would not be resigning, saying they were united by a “driving purpose” of “public duty”.
“We must prove that politics can be a force for good. I believe it can. I believe it is. We go forward from here. We go with confidence as we continue changing the country," he said.
He added that Labour's landslide victory at the 2024 general election would not have been possible without McSweeney, who led the party's campaign strategy.
“His dedication, his commitment and his loyalty to our party and our country was second to none. And I want to thank him for his service.”
Later today, the prime minister is expected to address Labour MPs as part of a wider bid to shore up his position.
Harriet Symonds is political reporter at PoliticsHome, where you can find the original version of this article