The Royal College of General Practitioners (RCGP) has expressed concerns that patients have not been properly informed about the care.data programme.
Leaflets about care.data, the NHS England scheme which would see patient data stored in GP practices placed into a central database, should have been sent to all households in England.
But the RCGP is worried not enough information has been given to the public, with only seven weeks until the national roll out.
RCGP honorary secretary Professor Nigel Mathers said: "The inevitable result of the failure to make the case for the scheme is the crisis of public confidence that we are now seeing.
"We urgently need a renewed national push by the authorities to ensure that patients are fully informed, in clear terms, about the benefits of the scheme, what their rights are, and what their rights to opt out are."
Mathers noted that even some GPs are "uncertain" about how the information will be safeguarded.
He said: "The College remains supportive of the care.data initiative in principle, as we believe that it will help the NHS improve the quality of care for patients and to better prepare for outbreaks of infectious disease, such as flu, through for example, the use of shared suitably anonymised data to build up a picture of which treatments work best.
"However we urgently need reassurance about what plans are being made to address current GP and public concerns to restore public confidence in the scheme."
The RCGP has called on the government and NHS England to act immediately, warning that otherwise "further questions will inevitably be asked about the wisdom of rushing the scheme through".
Mathers said: "It would be a tragedy if something that could have enormous benefits for patient care falls at the first hurdle because of a failure of communication.
"It is vital that patients and doctors are as informed and as confident as they can be in the scheme, and in the safeguards in place to ensure patient confidentiality, before it is introduced across England.
"We have been informed by NHS England that the Health and Social Care Information Centre does not make a profit from providing data to other organisations; that data will not be sold to insurance companies for the purposes of insurance and that confidential data can only be disclosed where allowed by the law."
The RCGP has produced guidance about secondary uses of data, which can be found on their website.