Dirty ambulances could be spreading infections because crews do not have time to clean them between call-outs, unions have revealed.
The new alert comes two years after a report claimed the government's failure to tackle ambulance cleanliness was a major flaw in its infection control policy.
General secretary of the Ambulance Service Union Steve Rice said cleaning practices across ambulance trusts were 'ad hoc'.
'Staff haven't time to clean their vehicles. After every call it needs to be done again, but staff aren't given any time to do that.'
Ambulance staff need 20-30 minutes to clean vehicles properly, he said. He added that hospitals were refusing to lend ambulance staff mops and buckets, fearing cross-contamination.
He recommended every accident and emergency department having a sluice for ambulance crew use.
A Unison report two years ago found ambulance cleaning in some parts of the country was 'rough and ready' and recommended more rigorous national standards.
Unison's national ambulance sector committee secretary Sam Oestreicher told HSJ: 'The problem hasn't been addressed.'
'Demand has gone up 100 per cent over the last 10 years but the resources have not increased to the same level. It needs some recognition by the government,' he said.
'MRSA could be spread by ambulances, but when the pressure is on the cleaning is cosmetic at best.'
He added concerns about cleanliness of patient transport services, which are privatised in many areas. 'We want to see some proper monitoring.'
Currently, trusts issue their own guidance along with guidelines from the Ambulance Service Association.
The ASA recommends that after each patient journey, the inside of ambulances should be totally decontaminated of bodily fluids, with detergent wipes used on all surfaces and bedding changed.
Exteriors should be cleaned with detergent, followed by a full disinfection whenever they have come into contact with bodily fluids.
Hilary Pillin, ASA health and safety co-ordinator until the ASA was absorbed into the NHS Confederation last month, said cleaning was down to individual trusts.
'It should be possible to do what's required within a minimum time frame,' she said.
'Trusts should be encouraged to do their own auditing, which may not always be happening,' she said.
Ms Pillin admitted that the ASA health and safety committee had not met for eight to nine months because of uncertainty over the organisation's future.