Boris Johnson’s mobile number has been published online for the past 15 years, it has emerged amid reported fears inside No10 that the PM’s contact details are too widely circulated.

The PM’s refusal to change his old digits is reported to have been a source of consternation inside Downing Street – an issue that has grown in prominence amid government lobbying scandals after it was discovered billionaire James Dyson had personally messaged him about a tax issue last year.

However his attachment to the 11 figures has meant internet users have been able to find a direct route from their phones to Downing Street after finding the PM’s direct line in an old press release acquired by The Independent and first hinted at in the Popbitch gossip email.

Despite more than a decade with the same number the PM appears to have shown little interest in redecorating his digital persona. On Whatsapp, which the PM is known to make use of, his profile is accompanied by the default image and ‘about’ message offered by the application.

It is understood security at No10 are now involved following the revelation, and that the phone number was still in use by the PM this evening.

Mr Johnson, who has had the same digits for more than a decade, is reported to have previously been urged by top civil servant Simon Case to change his number due to the ease with which lobbyists, business figures and others may have in contacting him. The PM is understood to have ignored the advice.

It comes as Mr Johnson and his government are mired in allegations of sleaze over the access of lobbyists in Whitehall and renovations to the PM’s personal flat above 11 Downing Street.

Earlier this week the Electoral Commission announced it would investigate how he paid for the expensive redecoration, which some reports suggest cost up to £200,000.

Meanwhile on Wednesday Sir James Dyson denied trying to “extract favours” from the PM after a text exchange between the billionaire and Mr Johnson was leaked to the public.

The messages showed the Brexiteer businessman receiving assurances that his overseas staff would not have to pay additional tax if they came to the UK to work on a ventilator project as part of the UK’s Covid-19 response, with Mr Johnson saying he would “fix” the issue.

Downing Street has been approached for comment.