After railing against the slovenly attitude of car makers, legislators and parents towards child car safety last November, I was inundated with letters from worried mums and dads.

Since then two car-makers, Renault and Volvo, have launched a range of children's seats specifically designed for their cars (although when you realise that the Renault and Volvo versions are identical you wonder just how "specifically designed" they are). More and more car makers are also selling "approved" baby seats, usually made by specialists such as Britax. Slowly but surely, parents are getting the message: children are not safe in a car unless they are properly belted.

Yet although experts reckon that 70 per cent of all British children are now restrained in a car, in two out of three cases the restraint system is used incorrectly. In other words, only 23 per cent of Britain's children sit safely in cars.

The Government is not helping. Although it happily spends millions on yet more drink-drive campaigns (even though the evidence is that the message has got through loud and clear), and on its latest anti-speeding campaign, it has never initiated a belt-up campaign for kids. One reason may be that, amazingly, there is still no legal compulsion for under-three-year- olds to use child seats.

It is simple to sit safely, in a modern car, if you are an adult. You simply do up your seat belt. The belt, the seat, the impact resistance of the car and, if it is a new vehicle, the airbag, are all designed and rigorously tested to protect you, the adult. With children, such rigorous testing just is not done. Manufacturers claim there are just too many variables. A baby reacts differently from a toddler, who is different from a five-year-old.

Baby seats, unlike adult car seats, are not made by the car manufacturer. To put every child seat through every crash test cycle in every car model would be an expensive and time-consuming procedure that no motor manufacturer is prepared to go through. In addition, many of the new safety breakthroughs in cars can actually be dangerous for children. Airbags, for instance, are lethal to babies in rear-facing seats.

To make matters worse, child seat manufacturers are usually kept in the dark by the car makers. Britax (which has more than 50 per cent of the UK market) sees new car models at about the same time as we punters. Existing seats usually fit new models, although sometimes the manufacturers bowl the child seat specialists a googly.

Ford, when it developed the Mondeo, changed the bolt dimension in the seat belt anchorage, which meant that the standard fitting kit did not work. However, it did not bother telling the child seat makers.

Nowadays, fitting kits are rarely sold. It is much more common for parents to buy seats which can be moved from one vehicle to another, and then tethered by the adult belts.

Once again, though, manufacturers design belts for adult use, not for children. Makers are increasingly siting their buckles further forward, the better to grab the adult's hips in the event of an accident. The trouble is, when the buckle is sited further forward, the belt usually does not grab the child seat as tightly. Britax cites all Peugeots, Land Rover Discovery, BMW's best-selling models (the 3- and 5-series), Proton and some Volvos as being particularly difficult. Some front seat belts are too short to tether baby seats: Britax reckons some Volvos and Hondas are problems here.

A further worry is the long stalk to which many seat belt buckles are fixed. Long stalks often make the buckle rest on the frame of the child seat. This should be avoided, says Britax.

Car dealers usually stock a range of manufacturer-approved car seats, invariably made by specialists and usually tested by the makers. The other way to ensure that the seat you are thinking of buying will fit a certain car is to ring the seat manufacturer. Britax has its own customer service number. For no charge, you will be advised what sort of seat to buy, depending on the weight of the child and the type of car.

Testing out the new Volvo-Renault range of children's seats, I found the Argonaut seats fiddly to assemble - and impractical if your child seat is used in different cars. More practical is a booster seat for 18kg to 36kg children (about three to 10 years) which not only has the under-bottom booster, complete with wings around which to feed the lap part of the belt, but a backrest featuring side head protection and upper wings to route the diagonal strap of the belt. The back rest is adjustable, and it will fit most cars - not just Renaults and Volvos. One final piece of advice on Renault-Volvo child seats: Renault dealers charge much less for these seats than do Volvo dealers.

As a general rule, try to avoid buying child seats through dealers. They invariably charge more than high street retailers such as Mothercare or Halfords. The Renault-approved forward-facing Britax Freeway seat (for children nine months to four years) costs £99.29 in your local Renault garage, but £89.95 through Mothercare.

Here are a few simple extra rules:

Never buy secondhand unless you know the seat's history. It may have been involved in a big shunt, damaging its safety. Similarly, if you have a big accident, get a new seat.

The safest place to put your child is in the central rear seat: there is less likelihood of side impact injury. A two-point (lap) belt, as usually supplied in the central rear position, is as good as a three-point belt when securing a baby seat. For seat designs where the adult belt actually tethers the child, use a three-point belt.

Ensure the harness securing the child is done up tightly. Equally, make sure the belt securing the baby seat is tight. Too much slack in the belt is the commonest cause of misfitting and of potential danger.

Ensure that the seat meets the British Standard and - increasingly more widely used - the European Standard (ECE 44).

Above all, ensure children are properly belted in their own seats. A small child held in the arms of an adult, whether or not the belt secures both child and adult, is not protected. Kinetic energy transforms a 25kg child into a one-ton mass in a head-on 30mph impact. You will never be able to hold on to your child. And if you are both in the belt, you will probably end up squashing your child to death.

Britax's Helpline: 01264 386034

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