Close Starmer ally Ben Nunn appointed as Rachel Reeves’s chief of staff

One of Keir Starmer’s closest allies has been appointed as Rachel Reeves’s chief of staff in an effort to further strengthen ties between Downing Street and the Treasury, the Guardian understands.

Ben Nunn, who worked with the prime minister in opposition and is one of his most trusted advisers, will begin his new role with immediate effect.

He was previously the chancellor’s media special adviser and had been closely involved in preparations for the budget later this month, in which Reeves is expected to put up income tax in a breach of a Labour manifesto promise.

Those plans are understood to have been agreed by the budget board, a group of advisers from across Downing Street and the Treasury who meet regularly to discuss the chancellor’s options.

In his new role, Nunn, 38, will play a key role linking the two operations, having worked closely with both senior politicians, becoming one of Starmer’s few trusted allies at Westminster.

A senior Downing Street figure said: “Ben is highly respected across government and this new role is a testament to that. As chief of staff, he’ll be the bridge between No 10 and No 11 and a close confidante to the prime minister.”

Nunn is understood to have had discussions with the prime minister and the chancellor over the autumn about taking on a more senior role in government. At one point the options included a post in No 10. He will work now closely with Starmer and his chief of staff, Morgan McSweeney, as well as the chancellor.

Labour insiders believe he will build on the more collaborative relationship between No 10 and the Treasury to prioritise the domestic economy as an issue within Downing Street, as well as help to avoid damaging political decisions like last year’s winter fuel allowance cut.

Katie Martin, who held the chief of staff role for almost five years, will take on a new role in the Treasury focused on strengthening the government’s frayed ties with business.

Reeves said: “Katie Martin has been my most trusted adviser for nearly five years and I’m delighted she will continue to support me in government, playing a central role as my business adviser. Labour won the election last year in no small part because of her leadership and dedication.

“Ben has been a pivotal figure in the Labour party and this government over the past decade. His insight, expertise and strategic thinking will be essential as we continue to focus on building stronger foundations to cut NHS waiting lists, cut the national debt and cut the cost of living.”

Martin will remain as a special adviser until the end of the year before starting her new role as the chancellor’s business adviser in January.