BBC News Online examines what the ratings actually mean and whether they matter.

What are NHS star ratings?

The NHS star ratings were first published in 2001. Hospitals and other health care providers are rated in much the same way as hotels every year.

They are awarded zero, one, two or three stars. The best trusts receive three stars, the worst get none.

In recent years, officials at the Department of Health have rated hospitals.

This year, for the first time, that job was given to the independent watchdog the Commission for Health Improvement.

How are health providers rated?

Hospitals, primary care trusts and ambulance trusts are assessed against key government targets.

Acute hospitals were judged on 45 different criteria, ranging from the length of time patients wait for operations to cleanliness.

Primary care trusts were judged on 46 targets, ranging from the length of time patients wait to see a GP to staff sickness absence rates.

Ambulance trusts were assessed on 13 different criteria, including the length of time they take to respond to emergency calls.

Mental health trusts were judged on 30 targets, including patient suicide rates and the quality of their hospital food.

Do the ratings provide a good overall picture?

Very few people outside the government believe the star ratings provide an accurate picture of how the NHS is doing.

The Commission for Health Improvement acknowledges that they provide only "a snapshot".

The British Medical Association has suggested they "measure little more than hospitals' ability to meet political targets".

It points out that the ratings fail to reflect the quality of patient care or survival rates.

Hospitals and others were also given advance notice of what targets were being assessed.

Many of the targets, such as A&E waiting times and ambulance response times, have also been ridiculed in recent months.

An official survey of A&E departments in March found 85% were treating patients within four hours. Hospitals had been given advance notice of the audit.

However, a second survey by the BMA the following week found that just 63% were meeting the government's target.

A recent report by the independent watchdog, the Audit Commission, suggested the NHS was wasting millions of pounds trying to meet "piecemeal" targets.

It also raised concerns over whether recent improvements, such as cuts in waiting times, can be sustained in the long-term.

Who cares about NHS star ratings?

Despite their unpopularity, star ratings are important to many people.

The government believes they can be used to gauge improvements in the NHS. It also uses them to identify trusts that need special help.

For instance, trusts that get zero stars are expected to draw up action plans to improve their services. Its management team can be replaced if they fail to deliver.

Ministers also use the ratings to reward the best trusts. They receive additional money for patient services. This year, they are also being invited to apply to become foundation trusts.

The first wave of foundation trusts are scheduled to come on stream in April 2004.

These elite trusts will have greater freedom from Whitehall control and will be able to raise extra money for patient services.

Trust managers acknowledge that star ratings can also affect staff morale.

There is anecdotal evidence that they can affect patients' perspectives of hospitals, with some preferring to be treated at three star rather than zero star trusts.

Are star ratings here to stay?

The publication of NHS star ratings are greeted every year with calls from doctors and opposition MPs for them to be scrapped.

However, ministers see the ratings as a key element in their NHS modernisation programme.