England's National Data Guardian has advised the UK government that public and professional trust should carry substantial weight as it decides the future of the NHS Federated Data Platform, the data system supplied by U.S. company Palantir, in a letter published Monday on GOV.UK. The advice makes trust and national control over data explicit criteria in a major public-sector technology contract, a test case for U.S. vendors that hold sensitive government data in allied countries.

What Happened

Dr. Nicola Byrne, the National Data Guardian for Health and Social Care, wrote on Oct. 9 to James Frith, minister for health innovation at the Department of Health and Social Care. The contract for the Federated Data Platform, known as the FDP, was awarded in November 2023. With decisions about its future approaching, Byrne's letter offers three pieces of advice.

First, trust should be given substantial weight when evaluating any supplier of a system that handles health and care data. "Commercial strength and technical capability must not outweigh whether the public, professionals and end-user organisations trust the arrangements," she wrote. Second, decisions should rest on clear, objective evidence of the platform's benefits and limits, communicated openly. Third, concerns about interoperability, vendor lock-in and data sovereignty must be addressed, including by considering open standards and open-source technology.

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The GOV.UK summary stresses that Byrne supports the platform's goals and does not recommend a particular contractual outcome. She asked the minister for a response.

The Evidence

The letter acknowledges that more than 80% of secondary and tertiary NHS care providers have signed up and that some trusts and patients report benefits. Organizations that use the platform want to keep it, and continuity and the cost of change matter to them, she wrote. But more than 100 NHS data and digital professionals signed a letter objecting to continuing the contract, and assurances about technical, legal and contractual safeguards have not eased public concern about the supplier, which she said has grown since the contract was awarded.

Byrne cited several outside sources. Research commissioned by Understanding Patient Data analyzed 1,329 health-data media articles from March 2025 to June 2026 and found 243 about Palantir or the FDP, 84% of them negative. A July 2026 YouGov survey of 2,097 UK adults, commissioned by the campaign group Eko, found 76% considered it unacceptable for U.S. technology firms to handle NHS patient data.

The rate at which people register a National Data Opt-Out, which limits how their health data is used, rose distinctly in May and June 2026 after stable levels in 2025. Byrne said causation cannot be established but the rise coincided with media coverage of the FDP. In polling by Understanding Patient Data, 41% of people who recalled Palantir coverage said it made them more likely to opt out or stay opted out.

Two House of Commons committees have urged action. The Science, Innovation and Technology Committee recommended in June that the government exercise the February 2027 break clause in the contract, and the Health and Social Care Committee echoed that in July. The government's response acknowledged concerns about mistrust but said there was no evidence of a significant impact on opt-out rates.

The letter does not include a response from Palantir.

Why It Matters

Opt-outs are the practical risk. Byrne warned that further increases could make national health data less complete and less representative, weakening research, planning and service improvement. She also said answering public concern about the supplier takes up significant staff time, even in organizations that have not adopted the platform.

For governments buying cloud and data platforms, and for vendors selling them abroad, the letter sets out a standard in which public confidence and data sovereignty sit alongside price and capability. Byrne's call to consider open standards and open-source technology also signals pressure to reduce dependence on any single supplier.

What to Watch

The government must decide before the February 2027 break clause whether to continue with Palantir. Byrne noted that the independent evaluation by Imperial College London and a National Audit Office study of patient data integration will not conclude in time to inform current decisions. Watch for the minister's reply, the next National Data Opt-Out figures and any public response from Palantir.