Coach companies are sidestepping the new legislation by fitting speed limiters to their vehicles and having them reclassified as buses and so avoiding costly safety modifications.
Operators contracted to at least three local authorities - two in the Midlands and one in Wales - are exploiting this loophole in the law to keep costs down, The TES has learned.
Coaches brought into service after October 1988 and minibuses carrying children will have to be fitted with seat belts as from February 10. Older vehicles do nothave to be adapted until February 1998. Vehicles incapable of exceeding 60 mph are exempt from the rules.
"Our main worry is that most of the belts that have already been fitted are not necessarily fitted safely," said Pat Harris of the pressure group Belt Up School Kids.
Seat belts installed in minibuses which had been adapted from vans were insecure and could be ripped out in a collision, she warned. Many coaches were being fitted with seat belts designed for cars which were not crash tested and quite unsuitable for the purpose. In an accident these could cause internal injuries to children wearing them, she said. "We think there will be accidents in the future in which these belts will seriously injure children or even kill them."
She said that operators which made safety a priority were being undercut by less scrupulous companies and losing business with local authorities as a result.
David Rogers, road safety adviser to the Royal Society for the Prevention of Accidents, said: "The more cash-strapped councils will be looking for loopholes. We are concerned that if councils try to cut costs they might opt for people running buses rather than coaches and will be able to get round the rule of having seat belts fitted. If that happens we are losing all the benefits that might have accrued from this legislation."
He called on the Government to tighten up the legislation so that the seat belt installation was checked as part of vehicle MOTs. Volunteer parents or trained escorts should travel with children to make sure they were wearing the belts, he said. "It's not cheap but no safety gain is. We know that parents are willing to pay for their children to travel safely to school."