I urge researchers responding to the call for information about sharing data sets (M. Bobrow Nature 500, 123; 2013) to defend the important principle of informed consent by patients participating in medical research.

The UK Health and Social Care Act 2012 requires the transfer of all National Health Service electronic medical records in England from general practitioners to the Health and Social Care Information Centre. The biomedical research charity the Wellcome Trust and the Human Genomics Strategy Group have proposed that variant files, which contain whole human genomes minus the Sanger Institute reference genome, should be attached to the records.

The UK government's intention is to share these data with accredited researchers — ranging from the Google-funded gene-testing company 23andMe to private health-care companies and Chinese research institutes — but without people's knowledge or consent.

Most data will be 'pseudo-anonymized', with some identifiers (such as names) stripped out, but with the ability to link back to the individual retained. People can opt out of this data-sharing system (see go.nature.com/azkyru), but that will in effect prevent members of the public from taking part in medical research.

Abandoning informed consent is unlikely to benefit biomedical research (J. P. A. Ioannidis Am. J. Bioethics 13, 40–42; 2013). Researchers could face a dwindling source of data as people withdraw from participation to protect their confidentiality.