LONDON — A veteran Labour minister rowed in behind Keir Starmer Monday, warning MPs and his top team to stop plotting to remove him as British prime minister.

Jacqui Smith, a Labour Party veteran who served in both Tony Blair and Gordon Brown’s governments, said it was a “good idea” for the prime minister’s chief of staff, Morgan McSweeney, to resign Sunday — but said Starmer must not follow him out of No. 10 Downing Street.

Starmer, whose authority was already dented by a rocky start to his premiership and poor opinion poll ratings, has been further weakened by his decision to appoint the former Labour peer Peter Mandelson as U.K. ambassador to Washington.

Speaking to broadcasters on Monday morning, Smith, an education minister in Starmer’s government, said MPs — and his Cabinet — must not now move against the prime minister.

“One of the mistakes of previous governments that it’s pretty important that this Labour government doesn’t fall into is the focus on infighting,” Smith told Times Radio.

“That I think would be a mistake and I hope that my colleagues don’t pursue that particular route.”

The previous Conservative government cycled through five prime ministers in just eight years before being voted out of office in 2024.

In a later Sky News interview, Smith also warned Cabinet colleagues to stop plotting.

They should “probably concentrate a bit more — and certainly they should get their advisers to concentrate a bit more — on the change we’re making to the country, rather than the change that might happen to the leadership of the Labour Party at some point in the distant future,” she said.

Starmer’s top team remains loyal in public, but some Cabinet ministers are voicing concerns about his future in private.

Downing Street hopes the departure of McSweeney — Starmer’s closest political adviser since becoming Labour leader, and a lightning rod for some lawmakers’ anger over the handling of the Mandelson scandal — will satisfy his critics.

McSweeney said Sunday he is stepping down after taking “full responsibility” for advising the PM to appoint the former Labour peer to the Washington role.

Mandelson, who was sacked last September over his friendship with convicted sex offender Jeffrey Epstein, is now under police investigation over alleged misconduct in public office after a tranche of documents in the Epstein files appeared to show he leaked sensitive documents to the late financier at the height of the 2008 economic crash.

But Andy McDonald, a member of the left-leaning Socialist Campaign Group of MPs, said Starmer’s “purge … of the left” needed to end and the “Mandelsonian agenda” hadn’t worked.

“It has caused us so much pain and harm and it’s diluted who we are as a Labour party,” McDonald told the BBC Monday. “We really do need more of a clear signpost and not a weather vane.”