Burnham exchanged messages with Trump chief of staff impersonator

Sources said a few messages of no significance were sent and the incident was quickly reported to the appropriate authorities.

A UK Government spokesperson said: “We do not comment on national security matters.”

The British embassy in Washington was so concerned it raised the matter with the White House, two officials told Politico, which first reported the exchange.

Later on Monday, a White House official told the outlet: “This incident has nothing to do with the chief of staff’s devices being hacked.”

Last year, The Wall Street Journal reported that the FBI had launched an investigation into efforts to access Ms Wiles’ phone after an unknown person contacted prominent Republicans and business chiefs while pretending to be her.

It is unclear when the messages were sent and what was discussed between Mr Burnham, who succeeded Sir Keir Starmer in Downing Street on July 20, and the impersonator.

Downing Street declined to say whether any measures would be taken to prevent a similar breach happening in future as it faced questions from journalists about the incident on Monday.

Mr Burnham is not the first high-profile British political figure to have come into contact with an impostor.

Footage of a hoax call in which then-foreign secretary Lord David Cameron believed he was speaking to former Ukrainian president Petro Poroshenko was released by the UK Government in 2024.

The Foreign Office said the perpetrators in that case were “clearly Russian” and made the incident public in a bid to pre-empt any effort to manipulate the video.

In 2022, then-home secretary Priti Patel and then-defence secretary Ben Wallace were also targeted by hoaxers suspected of working for the Kremlin.

In 1998, impressionist Jon Culshaw was put through the Downing Street switchboard to then-premier Sir Tony Blair while pretending to be then-leader of the Opposition Lord William Hague.

Sir Tony realised instantly the call was prank, but laughed and said: “It’s quite a good imitation.”