Officers from Avon and Somerset and Devon and Cornwall police forces and officials from the Department of Transport checked 236 coaches, buses and minibuses at four service stations between Bristol and Exeter on Saturday.
Operation Tourist discovered 118 vehicles were defective. Three coaches were ordered off the road immediately. Two had brake and exhaust faults and the other, which was carrying 46 children and which police described as 'a potential death trap,' had a serious oil leak which had contaminated the exhaust system and was in danger of catching fire.
Inspector Terry Beale, who co- ordinated the joint operation, said: 'I didn't expect all vehicles checked to sail through, but 50 per cent is a very disturbing figure.
'It is all too clear that bus and coach operators have allowed themselves to become complacent. The most frightening result was that of the coach carrying the children.
'These operators must realise that we entrust them with our lives and those of our children. We shall certainly be mounting more of these operations throughout the summer.'