Dr Nicola Byrne, the National Data Guardian for health and social care in England, has warned ministers that growing numbers of patients opting out of data sharing could damage the quality of NHS data. Palantir has responded by accusing her of being captured by campaign groups. The US company leads the consortium that supplies the NHS Federated Data Platform.

In a letter to James Frith, the health innovation minister, Dr Byrne said recent increases in the national data opt-out rate had coincided with media coverage of the platform and its supplier. She said further rises could jeopardise the quality of the shared national health data asset, with consequences for service improvement and planning. Nearly 100,000 people have used the opt-out service so far in 2026, with significant spikes in May and June.

Dr Byrne described the level of public opposition to the platform and to Palantir as striking for a software supplier to the NHS. She pointed to a perceived misalignment between the values of the company and those of the health service, and to questions of national data sovereignty. She has also said that the cause of the rise cannot be definitively established. The increases have coincided with coverage of Palantir and the platform, she wrote, and concern has grown since the programme began.

The platform itself sits outside the opt-out. The data guardian has said the national data opt-out does not currently apply to the platform, because it supports care delivery and operational management of NHS services and not secondary uses such as research and planning. The rise in opt-outs therefore affects data used for research and planning.

A Palantir-led consortium was chosen in autumn 2023 to deliver the platform under a contract worth up to £360m over five years, with an option to extend that to £480m. In March 2026 the NHS Chief Data and Analytics Officers Network raised its own concerns and objected to the government continuing the contract. Dr Byrne said the concerns of that professional group should be engaged with seriously, given its central role in determining whether the platform is adopted.

Ministers have acknowledged the problem. In a letter to MPs dated 21 August, Mr Frith wrote that he was concerned about mistrust of Palantir and its effect on people's willingness to share data with the NHS, and that it was also eroding the support of health professionals. He described a rise of about 60,000 opt-outs over recent months, which he attributed to increased media interest. He added that the NHS is not locked into Palantir, since it owns the intellectual property in the data models and products built on the platform and could migrate them elsewhere.

The Health and Social Care Committee has urged the government to cut ties with Palantir and to begin looking for an alternative, recommending that the product be dropped when a break clause in the contract arises in February 2027. The committee's letter says serious mistrust among the public has the potential to deter patients from sharing their medical data with the NHS. It has asked what advice the Department of Health and Social Care has received on the feasibility of appointing a new contractor by March 2027.

Questions about access to patient data have also featured in the dispute. Earlier this year the data guardian asked NHS England to explain how Palantir staff gained access to identifiable patient data in the platform, something she said her office had not been aware of.

Palantir's UK chief has urged the government to keep the contract as ministers explore whether to trigger the break clause. The decision on the contract, together with the opt-out figures that Dr Byrne has put before ministers, will determine how the NHS balances its digital programme against public willingness to share records.