More than a million people opted out of NHS data-sharing in one month in a huge backlash against government plans to make patient data available to private companies, the Observer can reveal.

The General Practice Data for Planning and Research scheme is now on hold with no new date for implementation, and NHS Digital has made a series of concessions to campaigners to try to salvage it.

Under the scheme, GP health data for everyone in England, with identities partially removed, would be made available to researchers and companies for healthcare research and planning. The scheme is more extensive than current GP data-sharing arrangements.

But after the proposals were quietly announced in May, doctors’ leaders objected to the short six-week deadline for the public to opt out of the scheme, while privacy campaigners warned the process to remove identities could be reversed.

The deadline was initially delayed to September, but an online campaign encouraging people to opt out grew over the summer. Government figures show that in May 107,429 people opted out. In June, a further 1,275,153 followed.

“We became aware of this latest GP [data] grab in late March,” said Phil Booth, coordinator of medConfidential, one of the groups most critical of the scheme. “We said ‘well that’s just going to blow up’ … and then it did blow up, exactly as we predicted.

“People do care about their GP records and their medical confidentiality. And there is a simple straightforward thing that they can do, which is to tell their GP ‘please don’t let my data be used in this way’.”

NHS Digital announced in mid-July that it was abandoning the September deadline, and pausing the scheme, with no new launch date. It will soon start a “listening exercise” and consultation process before launching a public information campaign. In a major concession to critics, patients will now be allowed to opt out at any stage, with their data deleted even if it has already been uploaded. NHS Digital is also pledging to increase the security and privacy of the data, even while researchers are working with it.

An NHS Digital spokesperson said: “Patient data is vital to healthcare planning and research. It is being used to develop treatments for cancer, diabetes, long Covid and heart disease, and to plan how NHS services recover from Covid.

“Medical research and planning benefits all of us but is only as good as the data it is based on. The better the quantity and quality of data collected, the more useful it is for researching new treatments or for planning good, sustainable NHS services to meet patients’ needs, so it is vital people make an informed decision about sharing their data.

“We take our responsibility to safeguard data very seriously, and it will only ever be used by organisations that have a legal basis and legitimate need to use it for the benefit of health and care planning and research.

“We have listened to feedback on proposals and will continue working with patients, clinicians, researchers and charities to inform further safeguards, reduce the bureaucratic burden on GPs and step-up communications for GPs and the public ahead of implementing the programme.”

Booth said NHS Digital has “made a bunch of public promises and we very much want to see how those promises are delivered. We’ve always said there are fairly legitimate, ethical, research and planning uses that can be made of this data – it just has to be done right.

“The question is, what’s going on behind closed doors right now in terms of people lobbying against those [concessions] or for particular exceptions to them.”