More than a third of car seats could potentially be a serious threat to children travelling in cars, according to a recent Britax survey.

To help combat this, Mothercare is running a month-long car seat campaign. Running to May 23, the campaign aims to raise awareness of the dangers of second-hand and poorly fitted car seats. The focus of the campaign will be a nationwide car seat amnesty on May 20, supported by What Car? magazine, when parents can bring in second-hand seats and receive a discount on a new one.

The Britax survey found that 36 per cent of car seats required serious adjustment, or were completely incompatible with the car in which they were installed. A further one per cent of the seats themselves were found to be so damaged that they should not have been used again.

David Motton, of What Car?, explained the danger of damaged and second-hand car seats. He said: "Previous accidents can cause unseen damage. Unless you know the car seat history from day one, a second-hand car seat should never be used for your child."

Endorsed by What Car? as the expert retailer of car seats, Mothercare Home and Travel advisers have recently undertaken a national training programme updating their knowledge of car safety. As usual, Mothercare experts will be in stores on the trade-in day and throughout the month to advise customers. They will demonstrate how to fit the seat, then advise while customers try themselves.

Other activities in store include:

*A ten per cent discount on any new car seat on May 20 to anyone who trades in a second-hand car seat (excluding booster seats)

*In a total of 150 Mothercare stores, there are fitting devices to teach parents how to fit a seat

*Car seat safety leaflets can be picked up.

Mothercare will dispose of all second-hand car seats traded in on May 20 safely. The Oxford store taking part in Mothercare's car seat amnesty is at the Oxford Retail Park, Cowley. Tips for buying a child's car seat * Never use a seat that has been involved in any kind of car accident.

* Never buy or use a second-hand child car seat, unless you know its history, as the protective structure could be invisibly damaged.

* Never buy a seat until you have tried it in your car. Find a store where you can try before buying.

* Always choose the right car seat for your child's weight not age.

* Always ensure the car seat fits your car - each vehicle is different.

* Always ensure that the car seat is fitted properly. If you are unsure, take it to a Mothercare store for advice.

* Always keep the instruction manuals for future reference.

* Always ensure that the harness and chest pads are adjusted for your child's size every trip.

* Chest pads should be tight enough for two fingers to be inserted between the chest and the pad.

* Never use a car seat on a passenger seat fitted with an airbag.