Media playback is unsupported on your device Media caption The BBC's Fergus Walsh reports on why the rollout has been delayed

The start of a new NHS data-sharing scheme in England involving medical records is being delayed by six months.

Work to start compiling the largely anonymised records on to the Care.data database was meant to start from April.

But NHS England has now decided that will not now happen until the autumn.

The organisation has accepted the communications campaign, which gives people the chance to opt out, needs to be improved.

There has been widespread criticism that the public have been "left in the dark" over the plans amid reports not everyone received the leaflets explaining the project.

The Royal College of GPs, the British Medical Association and patient watchdog Healthwatch England have all voiced concerns in recent weeks.

The central database will involve taking records from GP practices and linking them with hospital records.

What is Care.data? When it is compiled, Care.data will be a giant database of medical records showing how individuals have been cared for across the GP and hospital sectors. Researchers believe the information will be vital in helping them develop new treatments as well as assessing the performance of NHS services. The records will be pseudonymised, which means the identifiable data has been taken out. Instead, it will just contain the patient's age range, gender and area they live in. Although, researchers can apply for those safeguards to be lifted in exceptional circumstances, such as during an epidemic. This will need the permission of the health secretary.

Experts say it will enable them to assess diseases, examine new drugs on the market and identify infection outbreaks as well as monitor the performance of the NHS.

To date information has been available about what happens in hospitals, but not what goes on in GP surgeries.

The information made available on the database will be stripped of identifiable data - although it will include the gender, age band and area a patient lives in.

However, concerns have been raised about the prospect of keeping all the information in one place, with campaigners saying that it could lead to privacy problems and data breaches.

There is a proposal - to be discussed next month and backed by NHS England - which could give non-NHS bodies, including private firms, the right to ask for access to the data.

NHS England has organised a mass mail-out to every household in England since the start of the new year, but there have been reports not everyone has received them.

Last week a BBC poll of 860 people found fewer than a third could recall getting them.

An NHS England spokesman said: "To ensure that the concerns are met, NHS England will begin collecting data from GP surgeries in the autumn, instead of April, to allow 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."

It has not yet been decided how the communications campaign should be built on - some have suggested there should be a high-profile TV and radio advertising campaign.

Dr Chaand Nagpaul, of the British Medical Association, said: "We are pleased that NHS England has listened to the concerns.

"With just weeks to go until the uploading of patient data was scheduled to begin, it was clear from GPs on the ground that patients remain inadequately informed about the implications of Care.data."

Association of Medical Research Charities chief executive Sharmila Nebhrajani said any sharing of data "must be done with care, competence and consent".

"Care that respects the sensitivity of the data, competence to ensure that information is held securely, and most importantly with the informed consent of the public," Ms Nebhrajani said.

She said a six-month delay to better explain the mechanics of Care.data could only be a good thing.

Nick Pickles, director of Big Brother Watch, said: "NHS England has failed to properly communicate to patients or GPs what this new database involves, how it affects our medical records and what the risks are.

"The scheme's benefits are no justification for not properly informing people what will happen and a delay is the right thing to do.

"Our medical records contain some of our most private information and any changes to how they are used should not be rushed into."