The government's plans to put the medical records of 50 million NHS patients on an electronic database, is in danger of being boycotted by as many as two-thirds of family doctors.
In a climate rife with suspicion that sensitive personal data could be stolen by hackers and blackmailers, a poll found that 59% of GPs in England were unwilling to upload any record without the patient's specific consent.
The poll of more than 1,000 doctors was carried out by Medix, a healthcare research organisation previously used by the Department of Health to test medical opinion.
The poll revealed that three-quarters of family doctors thought medical records would become less secure when put on a database ultimately for use by NHS and social services staff throughout England.
Half thought the records would be vulnerable to hackers and unauthorised access by officials outside the NHS, while a quarter voiced concern over the risk of bribery or blackmail by people with access to the records.
Some 21% also had doubts that social services staff would honour confidentiality rules.
The poll found GPs increasingly concerned about the NHS plan to automatically upload the records of everyone who did not register an objection.
A campaign last year forced ministers to concede that patients should have the right to stop their medical files being passed from the GP to an NHS data warehouse known as the Spine but anyone not exercising this veto would be assumed to have given "implied consent".
A Medix poll a year ago before the government's concession found that 38% of GPs said they would not put clinical records on the database without getting a patient's specific consent, and 13% said they were unlikely to do so.
However, recent polls suggested these proportions had risen to 43% refusing to upload without specific consent and 16% unlikely to do so; another 30% were unsure or unable to comment, leaving only 11% who thought they were likely to comply with the government's proposal.
The high level of scepticism follows months of campaigning by NHS agencies to persuade doctors that the "summary care record" scheme would save lives.
In trials in Bolton fewer than than 1% of patients opted out and the first 50,000 summary records were transferred to the database, including details of medications and allergies.
The move has made the information available to doctors providing out-of-hours care and eventually security clearance will be needed for tens of thousands of NHS staff to access to millions of patients' files.
Many doctors believed patients' confidential records would be at risk and said the security of a national scheme could not be trusted.
The British Medical Association (BMA) said the government would not regain the confidence of the public or the profession unless it could demonstrate its systems were safe.