There are few things more terrifying to parents than the thought they could be exposing their children to unnecessary injury.

But many car owners are doing just that every time they set off to the childminder or the supermarket.

Most responsible motorists would not even consider transporting their children without first fitting a child seat. But few realise that youngsters' lives are still being put at risk because their safety seats are incorrectly fitted.

According to road safety experts, up to four out of every five child seats have been badly fitted a startling figure which will horrify many parents. But from today, concerned motorists will be able to check their young passengers are being carried in maximum safety. The Sitting Tight scheme being launched by Oxfordshire County Council, allows parents to get their child seats checked or even fitted free by trained mechanics.

The initiative is the brainchild of the council's road safety team and is expected to cut the number of injuries suffered by babies and toddlers in accidents.

The county council's principal road safety officer Ian Harris insisted that the introduction of child safety seats had dramatically reduced the level of injury suffered by child passengers.

But he said more could be done to protect them. He said: "There can be no doubt of the value of child seats in reducing injuries in car crashes, and the good news is that most people are using them. But because of the difficulties of making minor adjustments, many people are not getting the best out of their seats.

"It doesn't mean that people's seats are dangerous, but in the event of a crash, children are not going to get the best possible protection. Some of the injuries children are getting could be avoided."

He said poorly fitted seats could expose youngsters to bad bruising and internal injuries.

He added: "Fitting a seat can be confusing because of the wide variety of seats on the market, combined with the different makes and models of cars. "There are more than 120 seats on the market and the whole thing is a bit of a nightmare. Some seats fit perfectly in one model of car but not in another.

"Many people fit a seat, think it is OK and simply don't realise it is wrong. There are some minor faults, but some more serious ones which in the event of an impact would cause the seat to turn upside down.

"There is no doubt this is a lifesaving scheme. We have already seen some seats that would not have worked if they had been needed.

"We saw one that was even tied in with string. If there had been a collision, it would have gone through the windscreen with the child in it."

The initiative was launched at the Berinsfield Family Centre, and motorists were invited to take advantage of the occasion by taking their cars along for a free check. Roy Tudor Hughes, Oxfordshire county councillor for Dorchester, said Berinsfield had been the ideal place to start.

He urged parents to use the service, adding: "It costs nothing other than a bit of time, but it could save your baby's life."

One of the garages taking part is Humphris on Oxford's Rose Hill. Service manager Adrian Walton said a simple check on a child seat could make the difference between life or death.

He said: "At the end of the day we are talking about a child's life. There are a lot of seats that are not fitted properly and many people don't realise how important it is to make sure the straps are tight. "Having a seat is only going half way to protecting your child. Loose straps could cause much more serious injuries. You wouldn't leave half-a-dozen eggs rolling around on the back seat and the same principal applies to children."

He said car manufacturers had taken great steps to improve safety for drivers and adult passengers but said more should be done to protect children. He added: "It is frightening to see kids not being fastened in.

"Unfortunately child safety is not a priority for motor manufacturers. Not many have a keen interest in child passengers." Nineteen outlets most of them garages have already joined the initiative. Its members are scattered around the county meaning that most people are within five miles of a trained fitter.

Mr Harris now hopes Sitting Tight will continue expanding. Leaflets explaining the scheme and lists of members are available by calling 01865 815657.