A new report shows that 60% of GPs are reluctant to put patients' medical records on to a national electronic database because they fear they would not remain confidential.
A total of 43% of those questioned by research organisation Medix said they would refuse to upload the information without a patient's consent while an additional 16% said they would be unlikely to do so.
Only 11% of the family doctors who were questioned for the Guardian poll said they would be likely to follow guidance to upload information unless a patient objected.
Three-quarters said they believe records will be less secure on a national database which would be accessible to NHS and social services staff throughout England.
Half said they had concerns about people hacking into the system or officials outside the NHS getting access to records, while a quarter feared those with access might be vulnerable to blackmail or bribery.
More than a fifth said they thought social service staff would not keep the information confidential.
During trials this year in Bolton, Lancashire, patients were told their medical records would be uploaded electronically unless they objected.
They were able to check the details and ask for their entire medical history - or parts of it - to remain private.