Boris Johnson recently approached senior Saudi officials he had met when he was prime minister to pitch the services of a consultancy firm he claimed “could be useful” to the petrostate’s autocratic crown prince, Mohammed bin Salman, leaked files suggest.

Johnson, who resigned from government in 2022, appears to have led the newly formed company’s efforts last year to persuade the Saudi government to hire it to provide advice on reducing carbon emissions.

The revelations, contained in leaked documents seen by the Guardian, appear to show Johnson exploited contacts he had made in Downing Street for commercial purposes. They raise questions about whether he breached lobbying restrictions imposed on former ministers.

Johnson’s overtures to the most powerful figures in Saudi Arabia were for Better Earth, a little-known UK-based consultancy firm established by a Canadian mining financier, who co-chairs the company with the ex-PM.

The approaches included a lunch and meeting in a private members’ club with an influential Saudi minister whom Johnson had met while in government, files suggest.

Johnson also personally wrote a flattering letter addressed to Prince Mohammed, telling the de facto Saudi leader he was a “fervent admirer of the vision you have for the kingdom”.

The letter is contained in the Boris Files, a cache of leaked documents that shine a light on Johnson’s post-prime ministerial career. The files were obtained by Distributed Denial of Secrets, a US non-profit that archives data leaks.

The cache offers an inside view of how Johnson has forged a lucrative career in the private sector after leaving government, using his influence and contacts made while in public office.

Better Earth did not respond to repeated requests for comment. The Saudi government also did not respond.

Johnson did not respond to multiple requests for comment. After publication, he emailed a statement to the Guardian that did not respond directly to questions about his commercial approaches to Saudi officials he had met while PM.

The statement denied that his private office misused a subsidy scheme intended to support an ex-PM’s public duties. The public duty costs allowance (PDCA) should not be used for private or commercial purposes.

“This story is rubbish,” he said. “The PDCA has been used entirely in accordance with the rules. The Guardian should change its name to Pravda.”

Better Earth’s shareholders include seven close associates and advisers to Johnson, including two ex-Conservative ministers and Charlotte Owen, a 32-year-old former aide given a peerage by the ex-PM.

As prime minister and, earlier in his career, foreign secretary, Johnson engaged extensively with the government of Saudi Arabia, an authoritarian state that rights groups have long criticised for human rights abuses.

Johnson met Prince Mohammed on a visit to Riyadh in 2022 and held a series of official calls with the royal while in Downing Street. The pair were reported to have frequently exchanged WhatsApp messages.

In his letter addressed to the crown prince last year, Johnson wrote: “I would very much like to explore whether [Better Earth] could be useful to you and the kingdom of Saudi Arabia in achieving your ambitions – because I believe it certainly could.”

Offer of employment

Better Earth was founded by a Canadian businessman, Amir Adnani, in late 2023. How Johnson first became involved with Adnani, who runs a multibillion-dollar uranium mining company and has appeared on the former Donald Trump adviser Steve Bannon’s podcast, remains unclear.

The Observer reported last year that a senior executive at Adnani’s US-based mining group met Johnson while prime minister in May 2022. Adnani posted on social media that Johnson and the executive discussed nuclear power and uranium.

Less than two years later, Adnani established Better Earth and hired Johnson, who had resigned as prime minister 15 months earlier, to serve as co-chair of the company, a part-time role for which he would receive £120,000 a year as well as an initial 12.5% stake in the business, files suggest.

The offer of employment was signed in late January 2024, a day after Johnson visited Riyadh, where he gave a speech and appears to have attended a dinner hosted by the UK’s ambassador.

According to the files, Johnson agreed to begin working for the company on 1 February. Days later, he completed an application form for the watchdog that monitors and approves post-government jobs, telling the body that he planned to start working for the firm in March.

“I was approached with an offer to be part of this new venture,” Johnson wrote in the application to the Advisory Committee on Business Appointments (Acoba). He said he would “represent the company at meetings with potential clients and investors”.

The form did not mention that Johnson had by then already agreed to work for the company.

When Acoba approved the role in April 2024, the watchdog imposed conditions, stating that for two years after leaving office Johnson “should not become personally involved in lobbying contacts you developed during your time in office in other governments” to secure business or investment for Better Earth.

However, Johnson had by then already had lunch with the Saudi minister of commerce, Majid al-Qasabi, whom he had earlier met in his capacity as prime minister, during which the new venture was discussed, files suggest.

Johnson met Qasabi on numerous occasions when in government. At least one meeting occurred at Downing Street, and documents seen by the Guardian suggest Qasabi oversaw Johnson’s trip as prime minister to the kingdom in March 2022. Official photos of the visit show Johnson on an evening tour of Riyadh’s streets with Qasabi walking at his side.

‘Friend’ in trunks

Leaked files suggest that after the February 2024 lunch with Qasabi, Better Earth planned for Johnson to send a letter to Prince Mohammed with the minister’s support. In an apparent reference to Qasabi, the company’s CEO wrote: “We have taken all the advice Majid has given us.”

Johnson appears to have then drafted formal letters to Qasabi and Prince Mohammed later in February 2024. They were prepared with an “Office of Boris Johnson” letterhead. It is unclear when or if they were ultimately sent.

Writing to the crown prince, Johnson referred to meeting Qasabi years earlier, recalling that his “friend” was “wearing a pair of floral swimming trunks … because we were both diving off the coast of what was then a trackless desert”.

Johnson continued: “Although I now live a life of blameless rustic obscurity in Oxfordshire, I remain deeply committed to carbon reduction.” He noted that he had “helped run the highly successful” Cop26 climate summit in Glasgow in 2021.

“I now chair a company that offers practical solutions for developing green energy and reducing carbon,” he wrote, explaining that he was “sending a more detailed note” about the company to Qasabi. “But it would of course be a great honour to come to see you and to explain in person.”

‘Keen to advise and assist’

According to a draft of the accompanying letter to Qasabi, Johnson said Better Earth was “keen to advise and assist” Saudi Arabia on preparing carbon reduction commitments for the UN’s Cop30 climate summit later this year.

He wrote that Better Earth was “not just an adviser but a project developer”. He said the company “would be honoured to send our team of experts” to the kingdom to evaluate opportunities to partner on developing “net zero geothermal electricity generation” projects.

“We would very much like to meet with the appropriate ministerial authorities,” Johnson said. “Our hope is to help [the crown prince] to achieve his ambitions.”

It is not clear if Qasabi passed on details of Johnson’s pitch to Prince Mohammed or how exactly the Saudi government, which is a close UK ally, responded to the overtures. However, Qasabi appears to have met the ex-PM several months later, in mid-June 2024.

Files suggest the meeting occurred at 5 Hertford Street, a Mayfair private members’ club owned by Robin Birley, a multimillionaire businessman and prominent Brexit supporter.

Writing to the club, Johnson’s assistant said: “Boris has asked if he might be able to use Robin’s study for a meeting,” and provided details of a small group of expected attenders. The list suggests Better Earth was on the meeting’s agenda.

As well as Johnson and Qasabi, Adnani, the ex-PM’s Canadian business partner, planned to attend alongside Chris Skidmore and Nigel Adams, two former Tory ministers who hold shares in Better Earth.