New research from the Department for Transport (DfT) says the use of such seats will reduce the risk of injury to children in the event of an accident.
It found that 63% of parents stopped using child car seats for their children when they were aged six or younger, one in 10 parents had stopped using child car seats for their children by the time they were three years old and only 41% of parents of children aged between seven and nine and just 26% of those with children aged 10 and 11 said that their child always travelled in a child car seat.
Road Safety Minister David Jamieson said: 'Child restraints play a very important part in keeping children safe inside cars. It is vital that they are fitted correctly and that they continue to be used for as long as is necessary.'
Marianne Le Claire, head of child safety research at TRL (Transport Research Laboratory), said: 'Children travelling in cars need to be in a purpose-built child car seat or booster until they are either 11 years old or 150cm tall.
Adult seatbelts will not fit them properly and will put them at higher risk of injury, in particular to the chest, lungs, abdomen and spine, in comparison to a purpose built child seat.
'However, if there is no alternative, restraint with the adult belt is better than no restraint at all.'