Ambulance trusts are among those rated

But what do they mean and do they tell us anything about the state of the health service?

What are NHS star ratings?

The NHS star ratings were first published in 2001. Hospitals, ambulances and primary care services in England are given hotel-style stars, which aim to show how well they are doing.

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

In previous years, the ratings were published by the Department of Health. They are now compiled by the independent NHS inspectorate, the Healthcare Commission.

How are health trusts rated?

The commission assesses each trust against a range of criteria, including key government targets.

Trusts lose stars if they fail to achieve these targets.

For instance, a hospital may lose a star if it fails to balance its books, keep its wards clean or treat patients quickly enough.

Ambulances may be downgraded if they fail to answer 999 calls quickly enough or take steps to improve the working lives of staff.

Primary care trusts may be marked down if patients are unable to see a GP within 48 hours or if services for drug addicts or for helping smokers to quit are deemed not up to scratch.

Mental health trusts may lose a star if they lack good outreach teams or effective plans for caring for patients.

The commission also assesses the "clinical focus" of each trust - how it monitors the care given to patients and how it tries to reduce clinical negligence claims.

It also examines "patient focus" - how trusts deal with patients.

For instance, trusts may lose marks if they fail to deal with complaints properly or if they don't allow outpatients to make appointments for days that suit them.

Are the ratings meaningful?

The government has said they are a useful way of tracking progress in the NHS and seeing if it is improving.

However, others disagree. One of the problems is that the NHS is given advance notice of what targets will be used to compile the ratings - critics say this might mean trusts focus on these areas, to the detriment of others.

Some areas, such as the number of hospital-acquired infections seen in a trust, have been introduced into this year's ratings

How important are they?

The ratings are used by the government and others to assess the performance of various parts of the NHS.

For instance, only three star hospitals are allowed to apply to become foundation trusts, which have much greater freedom from government control.

The ratings have also prompted ministers to sack NHS managers and send in trouble-shooters to zero-rated trusts.

Managers say the ratings also have an impact on staff morale.

Are they here to stay?

No. The ratings in their current form are now in their last year.

From next year, trusts will be asked to produce annual self-assessments, including comments from patient groups.