Andy Burnham exchanged messages with someone impersonating Donald Trump’s chief of staff, the Guardian understands.

The prime minister was in contact with an unknown individual pretending to be the senior White House aide Susie Wiles before concerns were raised about the incident. No messages of significance were sent and the suspicious activity was quickly reported to the appropriate authorities, it is understood.

The British embassy in Washington was so concerned it raised the matter with the White House, according to Politico, which first reported the exchange. A UK government spokesperson said: “We do not comment on national security matters.”

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

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

There have been security concerns related to Trump’s White House, with the president’s personal phone number common knowledge among reporters covering US politics.

In December 2025, a US Department of Defense report concluded Trump’s defence secretary Pete Hegseth had endangered the lives of US service personnel when he discussed details for a military operation with fellow senior US officials in a group chat to which a journalist had been added.

According to a source, Hegseth violated departmental policies when he shared secret information in a Signal messaging chat in March of that year. The chat was disclosed after the then national security adviser Mike Waltz added a journalist for the Atlantic, having saved his number under someone else’s name. Besides Waltz and Hegseth, the group also included the vice president JD Vance and the CIA director John Ratcliffe.

The source said the report by the inspector general, the internal investigative agency for the Department of Defense, found the information Hegseth distributed was secret and could have endangered the lives of US troops if it had been intercepted by a foreign enemy force. CNN first reported on the contents of that report.

In March, citing multiple anonymous sources the Guardian has not been able to verify, the Atlantic reported that the White House had been told Trump’s contact details had been offered for sale to people seeking influence. “It’s honestly just wild,” one of them told the outlet. “I’ve heard of CEOs offering money for his number. I’ve heard of crypto bros offering cryptocurrency for it.”