Government plans to build 152 "super surgeries" throughout England will not by themselves improve the quality of healthcare provided to patients, a report by an influential think tank said on Thursday.

The government wants every local authority to build at least one polyclinic, grouping together a team of family doctors with nurses and other health services, and open seven days a week from 8 a.m. to 8 p.m.

The plans are opposed by the doctor's union, the British Medical Association, which says such large clinics would break the traditional relationship between patients and their GP.

Health think tank the King's Fund said that polyclinics could help reorganise health services around the needs of patients and deliver integrated care.

"However, the evidence suggests that in practice these opportunities are often lost," it said.

"Bringing together multiple services does not always result in better working practices between professionals, and there is no evidence that larger GP practices deliver higher quality care than smaller ones, although they may be able to offer a wider range of services."

The polyclinic programme is being led by Health Minister Lord Darzi, a leading surgeon brought into the government last year by Prime Minister Gordon Brown.

Darzi has been given the task of drawing up a blueprint for the future of the National Health Service, which celebrates its 60th anniversary in July.

The polyclinics are designed to make it easier for patients to access healthcare by offering longer opening hours than existing GP practices, as well providing health services currently only available in hospitals.

The King's Fund warned that a major centralisation of GP services into a small number of polyclinics would make it harder for patients to see their GP, especially in rural areas.

The government has promised that polyclinics will not be imposed where they are not wanted, a pledge the King's Fund welcomed.