Boris Johnson's mobile phone number was left online for 15 years, raising fears hackers could have accessed it

• UK Prime Minister Boris Johnson's mobile number was publicly available on the internet for 15 years.
• It raises concerns that spies could have hacked his phone.
• Johnson now appears to have switched off his phone.

UK Prime Minister Boris Johnson's personal phone number was publicly available on the internet for 15 years, raising concerns that his phone could have been vulnerable to hacking by foreign agents.

The prime minister's number was attached to the bottom of a 2006 press release that was published when he was the shadow education minister.

The press release, which was promoting a pamphlet written by Johnson, invited readers to contact Johnson "directly" on his House of Commons landline or on his personal number.

The presence of the number was first reported by Popbitch, a UK gossip newsletter. The press release was subsequently deleted.

"If his mobile phone number has been that widely available, you can't rule out that others who you really don't want to have his number like hostile states with sophisticated cyber capabilities or criminal gangs may have it as well," Peter Ricketts, the former UK national security advisor, told BBC Radio 4's "Today" program.

Labour MP Kevan Jones, a member of Parliament's Intelligence and Security Committee, told Politico: "This is extremely worrying with massive security implications."

The prime minister's use of his mobile phone has been under scrutiny in recent weeks after the BBC reported on leaked texts between him and the billionaire entrepreneur James Dyson.

Johnson personally assured Dyson that he would "fix" a tax issue for him, the report said.

Saudi Crown Prince Mohammed bin Salman also texted Johnson in an attempt to lobby him over an attempted takeover of the Newcastle football club, The Guardian reported.

Johnson was said to have been lobbied so often through his personal phone that Simon Case, the UK's most senior civil servant, had urged Johnson to change his mobile number because so many people had access to it, The Telegraph reported.

The Times reported that a welfare claimant was able to contact Johnson personally and ask for help with a benefit claim after a friend gave them the prime minister's number.

Johnson referred the issue to the Department for Work and Pensions, which resolved it, the report said.

It appears almost certain that Johnson will now have to change his number, which now redirects to an automated message saying: "This person's phone is switched off. Please try later or send a text."