BORIS Johnson’s former aide Dominic Cummings has been blamed for the leaking of the Prime Minister’s text messages.

An internal inquiry has been launched into how messages between the Prime Minister and billionaire Sir James Dyson were leaked to journalists.

But reports said Downing Street sources are pointing the finger at Cummings, who quit as the Prime Minister’s senior adviser last year following a behind the scenes power struggle in No 10.

The Times, Daily Telegraph and Sun all reported comments from an insider naming Cummings.

“Dominic is engaged in systematic leaking,” a source told The Times. “We are disappointed about that.

“We are concerned about messages from private WhatsApp groups which have very limited circulation.”

READ MORE: Boris Johnson told Sir James Dyson he would ‘fix’ tax issue in text

The source suggested the Prime Minister was “saddened” and Cummings was “bitter” after his exit from No 10.

The leak of the texts to Sir James, in which Johnson promised the entrepreneur he would “fix” a tax issue for Dyson staff working to develop ventilators at the height of the coronavirus crisis last year, was not the first time the Prime Minister’s messages have been made public.

Johnson was sent a text message by Saudi Crown Prince Mohammed bin Salman as a bid to buy Newcastle United ran into difficulties last June

A No 10 source told The Sun that Johnson “fears Dom was responsible for the text message leaks about James Dyson and Mohammed bin Salman”.

The Telegraph said it is understood Cummings would have had legitimate access to the messages while he worked at No 10.

“If you join the dots it looks like it’s coming from Dom,” a source told the newspaper.

Cummings has not responded to the accusations.

The former Vote Leave chief worked closely with Johnson on the Brexit campaign and was a major figure in No 10 after the Prime Minister took office.

The Prime Minister stood by him after Cummings found himself in the eye of a media storm after driving his family to County Durham during the coronavirus lockdown.

But Cummings was subsequently ousted from No 10 amid the fallout from an internal power struggle with the Prime Minister’s fiancee, Carrie Symonds.

READ MORE: Number 10 announces internal inquiry into Boris Johnson and James Dyson texts

No 10 had initially said there would not be a probe into how the exchange with Sir James was made public, but a change of course was announced yesterday as it said an internal inquiry will be led by the Cabinet Office.

The spokesman confirmed the inquiry will examine the source of leaks of Johnson’s private communication “as related to this issue of Dyson”.

The BBC reported that the messages between Johnson and Sir James were exchanged in March last year after the businessman was unable to get the assurances he was seeking from the Treasury.

Sir James, who has changed his main address in business filings to the UK from Singapore, wrote to the Treasury requesting that his staff would not have to pay additional tax if they came to the UK to work on the ventilator project.

But when he failed to receive a reply, Sir James reportedly took up the matter directly with the Prime Minister.

He said in a text that the firm was ready but that “sadly” it seemed no-one wanted them to proceed, to which Johnson replied: “I will fix it tomo! We need you. It looks fantastic.”

The Prime Minister then texted him again saying: “[Chancellor] Rishi [Sunak] says it is fixed!! We need you here.”

Two weeks later, Sunak told the Commons Treasury Committee that the tax status of people who came to the UK to provide specific help during the pandemic would not be affected.

Downing Street has said it will publish correspondence between Johnson and Sir James “shortly”, after the Prime Minister told the Commons he was “happy to share all the details” of the exchanges.