A new NHS computer database may threaten the privacy of patients' medical records, the BBC has learned.
There are fears patients will have no say over what details are stored
A senior Department of Health civil servant said people would not be able to decide what details were stored.
Critics said this went against earlier government assurances that patients would be able to veto the information.
The DoH said people could still discuss with their doctor what details were recorded and control who could access them - except in an emergency.
The database, which is being installed as part of the NHS's £6.2bn IT upgrade, allows staff to access medical records wherever someone is treated.
Experts have warned the final cost of the system could hit £31bn.
Phil Walker, the DoH's head of digital information policy, made the privacy claims in an e-mail to a Warwickshire GP, Dr Paul Thornton.
The BBC's Andrew Hosken said Mr Walker stated patients do not have any right to determine what information is recorded about them by doctors, or to veto how it is recorded.
The British Medical Association said this appeared to contradict earlier ministerial assurances that patients will be able to withhold sensitive information from the database, to be introduced later this year.
The BMA has called for the government to clarify the situation, in the wake of Phil Walker's e-mail.
Dr Thornton, a GP in Kingsbury in north Warwickshire, told Radio 4's Today programme he had concerns about the new system, which was due to be introduced by the end of the year.
He said: "The danger with this system is that there's no GP or other professional with the clear responsibility to protect the information they have collected, and therefore civil liberties are very much in jeopardy".
Health Minister John Hutton said patients would have the right not to have their medical records stored electronically at all.
A second option of sealing the most sensitive data in an "electronic envelope" for use only in emergencies was also being offered.
But Mr Hutton said: "I believe very few people will opt out of the records.
"I hope and believe that patients will want to be part of this because it will help to save people's lives."
Harry Cayton, chairman of the National Care Records Development Board, said the sharing of patient information would remain a matter between doctor and patient.
Mr Cayton said the board was hoping to publish a 'Care Record Guarantee' later this year, providing it received the go-ahead from ministers.
"That will set out for the public how their data is collected, stored and shared, and how they consent or refuse consent to do that," he told the Today programme.
Richard Granger, director general for NHS IT, said the scheme was more secure than the old paper records system.
Shadow Health Secretary Andrew Lansley said: "There are serious unresolved issues on patient confidentiality."
Liberal Democrat health spokesman Paul Burstow said: "Ministers must allay patients' concerns as soon as possible so that people know that they will have control over the information held about them."