The head of the first private firm to take over a GP surgery today denied the contract would drain resources from the NHS.

However, although Mike Parish, the chief executive of Care UK, said the company would not recruit GPs from "under-doctored" areas of Britain, he admitted staff from other parts of the NHS would work at its surgery and walk-in centre in east London.

Under a deal believed to be worth £5m over five years, the company will provide primary care services free to 7,000 NHS patients in Barking and Dagenham.

It will employ three GPs and seven nurse practitioners, who will also staff a walk-in centre dealing with 100 patients a day.

Professor Allyson Pollock, of the University of Edinburgh, told BBC Radio 4's Today programme that Care UK had "very little experience" of providing direct services for patients, and would use the contract to take resources away from the NHS.

"One has to see this against the background of major cuts and closures that are going on in the NHS," she said. "Care UK doubled their profits last year but, not only that, they have very little experience of providing direct NHS services of any kind.

"What they will do is ... take GPs and nurses from the NHS, because that's the only place where they are."

Ms Pollock said the contracts were "commercial and in confidence", and added: "What people don't realise is that these corporations are using GP practices as a loss leader to come in and take more and more of the NHS budget".

The deal - brokered by the government as part of an overhaul of family doctor services - will see the return of a Saturday morning surgery.

Mr Parish admitted doctors employed at the practice would come from the NHS, but said his company was filling gaps in NHS services.

"We have undertaken not to take any doctors from existing under-doctored areas, because that would just be just moving the problem around," he added.

The chief executive said that although his company - which was set up in 1994 and mainly runs care homes and private hospitals - aimed to make a profit, it had reinvested "at least twice" its level of profits into new services.

The government has named six pilot areas with few GPs per head of population for pilot schemes contracting out services to the private and voluntary sectors.

The Barking scheme, which opens in July, is expected to be followed by contracts in Hackney, east London, and South Sefton, Merseyside.