The government believes diagnostic and treatment centres will help to cut NHS waiting times.

BBC News Online examines what these new fast-track surgery centres will do and why they are controversial.

What are diagnostic and treatment centres?

Diagnostic and treatment centres are fast-track surgery centres. They will specialise in common operations for which there are currently long waiting lists.

The idea is that the extra capacity in the centres will mean that patients with, for example, cataracts, can have them removed with far less delay.

Currently, more than 50,000 older people are waiting over three months for cataract treatment - and one quarter of all people over 75 develop a cataract.

The government is paying out �52m to fund extra operations in existing NHS eye units and diagnosis and treatment centres (DTCs).

The government expects the number of DTCs will rise to 100 by 2006, carrying out not just cataract operations, but also more complex surgery such as hip and knee replacement.

Who will run these new centres?

So far, the government has set up 20 DTCs. All of these are owned and managed by the NHS.

Ministers have now announced that a further 22 centres and two mobile units will be run by private companies, some of which are based overseas.

Will the centres help cut waiting times?

The government certainly thinks so. According to ministers, they will carry out thousands of additional operations each year.

They say that the centres being run by private companies will provide 250,000 operations annually.

Of these, 115,000 operations would have been carried out by NHS hospitals anyway.

But the theory is that by allowing the DTCs to do these, this will free up hospitals to treat other patients.

Why are they controversial?

The new centres are controversial for a number of reasons, not least the fact that some will be run by private companies.

Trade unions believe allowing private firms to run the centres is a step towards privatisation.

There are also concerns over who will staff these centres. Private firms will be able to second NHS staff to work in their DTC.

As a result, many are concerned that this will lead to poaching from hospitals which are already struggling to keep doctors and nurses.

Others have warned that the centres could take business away from NHS hospitals.

Many hospitals depend on this money to balance their books. But they also use it to subsidise other more expensive treatments or research.

If the money that would normally go to them is diverted to DTCs they could lose out and could have to cut some services.

In addition, there have been claims that the centres, particularly those being run by private companies, will not provide value for money.

Will they provide value for money?

This is a thorny issue. Ministers obviously think so. However, others are not so sure.

They are particularly concerned about the privately-run centres.