Alan Milburn will has come under fire after inviting private healthcare companies to assist in cutting NHS waiting lists.

The health secretary formally opened bidding from UK and foreign private firms as the government sets up dedicated surgery units.

Ministers hope that privately-run clinics carrying out routine surgery and diagnostic tests will cut NHS waiting times.

But Milburn has backed down on an earlier pledge to bar the new units carrying out private treatment.

Initial plans for 13 conveyor-belt style units, carrying out 10,000 operations, such as hip replacements, are to be expanded.

It is thought that Milburn will announce plans for 23 new surgery units.

Overseas and British private healthcare companies are set to tender for the new clinics - which will cost the taxpayer £100 million.

The move comes as ministers attempt to meet the pledge that no-one should have to wait for more than six months for treatment.

But the plans to recruit profit-making firms have dismayed senior Labour MPs.

The chairman of the influential Commons health select committee, David Hinchliffe, believes the move amounts to a betrayal of Labour's political values.

"I just do not feel that this sort of thing is compatible with what the Labour Party has historically stood for," he said.

Hinchliffe's view is echoed by GMB union chief, John Edmonds. "People did not vote Labour to have the NHS carved up and sold off to the highest bidder," he said.

Former health secretary, Frank Dobson backs the idea of dedicated clinics to take the pressure off overstretched hospitals.

But he too is opposed to the involvement of private healthcare companies.

"Generally it's a good thing because these places will crack on with dealing with cold surgery. They don't have to deal with accident and emergency, and they can keep going even if there is a flu epidemic," he said.

"But I see no point in involving the private sector because it doesn't add to the number of doctors and nurses. Running one of these is a doddle compared with running a general hospital."