The NHS delayed for at least six months a controversial plan to share data from people's medical records on Tuesday following concerns from doctors and patients' groups, acknowledging there was insufficient public confidence in the scheme.

The postponement by NHS England was welcomed by critics who had complained too many people did not properly understand the planned new system and the reasons for its introduction, or how they could opt out. Under the original plan, the first medical records were to have been compiled by the care.data system from the start of April.

Supporters say that sharing data, which will include information from GPs' surgeries for the first time, as well as from hospitals, will make medical advances easier and ultimately save lives because it will allow researchers to investigate drug side-effects or the performance of hospital surgical units by tracking the impact on patients.

But privacy experts have warned there will be no way for the public to work out who has their medical records, or to what use their data will be put. There have been questions raised about commercial companies buying data.

Some doctors' groups complained that the scheme, while valuable, was poorly understood and badly explained by NHS England, which has said the majority of the data would be anonymised or made impossible for patients to be identified. All 26 million households in England were sent leaflets about the plan but polls showed about two-thirds of people had not seen them.

In a statement, NHS England said the collection of data from GPs' surgeries would now begin in the autumn – it did not give a more precise date – to permit "more time to build understanding of the benefits of using the information, what safeguards are in place, and how people can opt out if they choose to".

A delay so close to the proposed start of a major scheme is a significant embarrassment for the NHS and its attempts to inform the public about the benefits of the database. Labour's junior health minister, Jamie Reed, was quick to call the delay "another NHS shambles of this government's own making".

Tim Kelsey, national director for patients at NHS England, said: "We have been told very clearly that patients need more time to learn about the benefits of sharing information and their right to object to their information being shared. That is why we are extending the public awareness campaign by an extra six months."

The extracted information will contain a person's NHS number, date of birth, postcode, ethnicity and gender. Once live, organisations such as university research departments – but also insurers and drug companies – will be able to apply to the new Health and Social Care Information Centre to gain access to the database. Last year it emerged that the private health insurer Bupa was one of four firms that had been cleared to access sensitive patient data.

The British Medical Association said on Tuesday it had become increasingly plain that people did not know enough about care.data and even with a delay the database should only be implemented with proper public backing.

Chaand Nagpaul, chair of the BMA's general practitioner's committee, said: "While the BMA is supportive of using anonymised data to plan and improve the quality of NHS care for patients, this must only be done with the support and consent of the public, and it is only right that they fully understand what the proposals mean to them and what their rights are if they do not wish their data to be extracted."

The Royal College of GPs called on NHS England to use the extra time to clarify aspects of the system, for example whether amber data – anonymous but containing details that could potentially identify an individual – will be provided for commercial use, and that information to third parties would not be sold for a profit.

Professor Nigel Mathers, honorary secretary of the RCGP, has written to NHS England suggesting a more thorough public information campaign, including TV adverts and a letter to each patient affected.

He said: "We would like to thank NHS England for listening to the concerns of RCGP members and for acting so quickly to announce this pause. The extra time will provide it with the chance to redouble its efforts to inform every patient of their right to opt out, every GP of how the programme will work, and the nation of what robust safeguards will be in place to protect the security of people's data."

The scheme's rollout has been beset by criticisms about the clarity of the information provided to the public. Earlier this month, the information commissioner's office criticised the campaign for failing to adequately explain what data was involved and how patients could avoid their medical records being shared.

The delay came a day after the solicitors Leigh Day began a legal challenge on behalf of a campaign group, medConfidential, arguing the leaflet sent to households was misleading. The online campaign group 38 Degrees polled 150,000 people, of whom more than 90% said they would opt out.

Sharmila Nebhrajani, chief executive of the Association of Medical Research Charities, said care.data was a good idea in principle that had been "stymied by its execution". She said: "Charities and their supporting patient groups have always said that sharing data for research can be a really valuable opportunity to speed medical research but it must be done with care, competence and consent."