Peter Mandelson’s involvement with the US tech company Palantir must be exposed to full public transparency, campaigners have said, amid fears he may have leaked more sensitive information than is alleged in his emails to Jeffrey Epstein.

Palantir, an $300bn startup that provides military technology to the Israel Defense Forces and AI-powered deportation targeting for Donald Trump’s ICE units, has UK government contracts worth more than £500m. Global Counsel, a lobbying company Mandelson co-founded and part-owns, also works for Palantir.

The cabinet secretary, Sir Chris Wormald, is being urged to release information about Mandelson’s role when the British embassy arranged for Keir Starmer to visit Palantir’s showroom in Washington DC in February 2025 shortly after Mandelson became ambassador to the US.

Mandelson and Starmer met the company’s chief executive Alex Karp and were shown the company’s military technology. Karp signed a strategic partnership with the UK defence secretary, John Healey, seven months later and in January the Ministry of Defence (MoD) signed a £241m three-year contract with Palantir to “boost military AI and innovation”.

Foxglove, a fair tech campaign group, led calls for the Cabinet Office to release information relating to any involvement by Mandelson in the negotiation of Palantir’s contracts.

Alex Burghart, a Conservative MP and shadow chancellor of the duchy of Lancaster, also urged Wormald to review Palantir’s latest MoD contract “given the allegations now coming to light about Mandelson’s conduct”.

Starmer’s meeting with Palantir did not appear in the prime minister’s register of visits and was acknowledged only in subsequent disclosures, Burghart said. He said Palantir’s MoD contract “was granted by direct award” – without competition – and asked that the cabinet secretary check there were “no other such contracts, no other such undisclosed meetings”.

Calls for transparency came after Mandelson was apparently shown to have forwarded to Epstein highly sensitive information he received as business secretary under Gordon Brown in 2009, including government responses to the global financial crisis. Epstein received a prison sentence for child sex offences in 2008 but was able to keep working and Mandelson stayed in contact with him.

“In light of Lord Mandelson now facing investigation for allegedly leaking ‘sensitive information’ to Jeffrey Epstein, we believe it is important to examine whether similar behaviour took place elsewhere,” Donald Campbell, the director of advocacy at Foxglove, told Wormald in a letter sent on Wednesday.

Speaking in parliament, the former Labour leader Jeremy Corbyn called for an independent inquiry into the wider Mandelson affair and described “a gilded friendly web” around Mandelson “under which favours were done, contracts apparently awarded, this ghastly company Palantir trying to get hold of our National Health Service apparently at the behest of Mandelson and others”.

Palantir’s contracts with the UK government have caused controversy. The British Medical Association said last week that doctors could refuse to use Palantir’s £340m NHS federated data platform in some cases, in protest over the tech company’s role in facilitating ICE activity in the US.

Palantir was co-founded by the billionaire tech investor Peter Thiel who has supported Trump. Emails released by the Ministry of Justice suggest that Epstein also had a relationship with Thiel.

Chi Onwurah, the chair of the science and technology committee, said: “We have raised questions about Palantir’s public sector contracts, how and why they came about and whether the UK should be dependent on large, US-based providers. We will be publishing our findings shortly, but it is clear that the government should prioritise greater sovereign capability in emerging technologies, and review its dependence on these firms.”

While Mandelson resigned as director of Global Counsel in May 2024, he has continued to retain shares in the consultancy, according to records at Companies House.

“We need the full picture on Mandelson’s involvement,” said Campbell. “Anything else risks irreparable damage to public trust.”

Palantir declined to comment. Mandelson, the Cabinet Office and the Ministry of Defence have been approached for comment.