The Sun claimed the prime minister's personal number was revealed during a prank on social media, where audio of his phone ringing and his answer machine message were posted.

The paper also said it had verified the number and it was one he had used for many years, including when he was chancellor under Boris Johnson - though he was reportedly been given a new device when he took over in Number 10.

The claim comes after Mr Sunak faced criticism for not handing over all of his WhatsApp messages from the phone to the official COVID inquiry, having claimed he did not back up the app and had changed phones multiple times since the pandemic.

Read more:
By-election defeats leave Tories asking is this a re-run of 1992 or 1997?
PM puts by-election losses down to mid-term blues and 'local factors'

But the social media posts appear to show the device is still in operation.

A Downing Street spokesman told Sky News: "We don't comment on security matters."

It is the second time a prime minister's phone number has been discovered online, after in 2021 Mr Johnson's own digits were revealed to have been freely available on a website for 15 years.

The number had been listed at the bottom of a news release issued when the ex-PM was shadow higher education minister back in 2006.

Reports at the time said senior officials had already advised the prime minister to change his phone number due to concerns about security and how many people were able to contact him directly.

Mr Johnson also later claimed to the COVID inquiry that he was unable to provide all of his messages from the pandemic due to security concerns about turning the phone on, and later reports suggested he had also forgotten the PIN to gain access to the device.