The star rating is designed to give patients an idea of quality

The service lost one of the maximum three stars it was given a year ago and says it has not been given a reason.

Ambulance trusts across the country have been given a star-rating based on their performance against a number of key targets and indicators.

It is appealing before Friday's deadline, imposed by the Healthcare Commission.

Financial incentive

Every part of the NHS is assessed on all aspects of its performance and is awarded a maximum of three stars.

For those trusts who gain all three there is a financial incentive as each gets an extra �0.5m in their budget.

The ambulance service says the Healthcare Commission based its assessment on old information.

The regional health authority says it should keep its top-grade status.

The commission in turn says it is happy to discuss the reasons for its assessment during the appeals process.

The targets include whether ambulances responded to calls about life-threatening conditions within the government target of eight minutes.