East Midlands Ambulance Service bosses say nearly 500 of their 750-strong fleet of vehicles have passed rigorous checks on their cleanliness.

The service has been carrying out an audit on its ambulances after failing an inspection by watchdogs the Care Quality Commission.

Commission inspectors assessed four of its accident and emergency response vehicles and discovered they failed to meet Government regulations to protect patients and staff from superbug infections, such as MRSA and Clostridium difficile.

They said staff were reusing equipment which should have been thrown out and, despite deep cleaning, some ambulances were still dirty.

Emas was warned to clean up its ambulances, in August, but still failed to meet the grade at a subsequent inspection.

Emas chief executive Paul Phillips apologised for the inspection failures but said he intended to stay in the post to improve the service despite calls from patients' groups for him to be sacked.

He said: "I was disappointed to learn the CQC's inspection identified four vehicles where we are still falling short on infection prevention and control standards.

"That situation is not acceptable and since the inspection, we have redoubled our efforts with our deep cleaning teams, investing almost £300,000 additional funds in this area.

"We are now carrying out a comprehensive audit of our ambulances, and so far have found 495 ambulances to be compliant in relation to issues such as clean internal surfaces and thorough cleaning of reusable medical equipment."

Emas has until December 14 to improve, or it could face heavy fines or prosecution.

An Emas spokesman said he could not produce a figure for how many accident and emergency ambulances are in the 750-strong fleet.