The Prime Minister’s director of communications has become the latest senior Downing Street aide to resign in a blow to Sir Keir Starmer.
Steph Driver announced she would be leaving her post on Thursday after almost five years working at Sir Keir’s side.
Ms Driver said the Labour Government continued to have her "unwavering support" as she announced her departure.
"Steph Driver has been a loyal and valued member of my team for almost five years,” the Prime Minister said.
"Steph played a leading role in transforming the Labour Party and delivering our historic general election win. I will for ever be grateful for her calm, wise counsel, leadership and humour. I wish her all the best in her undoubted onward success."
Ms Driver added: "It has been an honour to work with and advise Keir through opposition and into government.
“Being part of the team to rebuild and rebrand the Labour Party before securing an historic general election victory is an achievement and experience like no other.
"I'm also proud of what this government has already delivered, and thank the sharp and talented No 10 press team for their hard work and support during my tenure.”
It is the latest blow to Sir Keir and comes as Labour MPs are reeling over high-profile sackings and resignations in recent months, including Angela Rayner who quit as Deputy Prime Minister following a tax scandal and Lord Mandelson being fired as British Ambassador to the US.
Number 10’s Director of Strategy Paul Ovenden quit this month after “sexually explicit” messages he wrote about Labour MP Diane Abbott were uncovered.
The former Sunday newspaper journalist began working for Labour in 2014 and was a close ally of both the Prime Minister and his chief of staff Morgan McSweeney.
James Lyons, who was the No 10 director of communications for strategy, also left after only a year in the job.
Ms Driver’s predeccesor, Matthew Doyle, quit in March after nine months in the role.
Mr Doyle, who served as Sir Keir’s communications chief in opposition with Ms Driver as his deputy, stepped down immediately after feeling he had stabilised the Government’s communications strategy following a rocky first few months in office.
