All of the region's ambulances were deep-cleaned following the report
An ambulance service criticised for having dirty vehicles and putting patients at risk of infection has implemented a clean-up.
Nine out of 22 North West Ambulance Service (NWAS) vehicles were "in a very poor condition with visible dirt".
The Care Quality Commission (CQC) found the other 13 were not cleaned to a good standard and one was so unclean it was taken out of service.
The NWAS now has "robust systems" for cleanliness and hygiene, it said.
The NWAS covers the Cumbria, Lancashire, Manchester, Merseyside and Cheshire areas.
Inspectors found most staff were unaware of the ambulance service policy on cleanliness on its initial visit in the summer.
However on its return visit earlier this month, the CQC said the ambulance service had addressed all the areas of concern.
The ambulances inspected were found to be clean and 87% of staff had undergone training on cleaning procedures.
Darren Hurrell, chief executive of NWAS, said: "The findings are a positive reflection of the dedication of all trust staff who have worked extremely hard during a time of great pressure on our emergency service to ensure we are fully compliant with the government regulation on infections.
"We are, however, far from complacent, infection control remains high on our list of priorities."