Many parents are still flouting the new child car seat regulations which took effect in autumn this year.
As many as 65% of parents have not fitted child seats correctly, a survey by What Car? magazine found.
And only 35% know the specifics of the new regulations which are aimed at reducing the annual toll of 2,000 child deaths and injuries.
The law about children and car seats changed on September 18. All children must now use a child seat until their 12th birthday or when they reach 135cm (about 4ft 5in) in height, whichever comes first.
What Car? editor and father-of-three Steve Fowler said: "Nobody would knowingly put their children at risk, which is why we find it hard to believe how ill-informed parents are about how to fit child seats correctly. Parents need to take more responsibility for the safety of their children in cars."
In the summer the Government spent £600,000 on a publicity campaign to tell parents about the new laws but What Car? said its research showed that many had still not got the message.
Mr Fowler added: "If the Government is serious about its new legislation it should step up its publicity with television advertising so all parents are clear about the new laws."
Under the new laws, the driver of the vehicle is the person responsible for the safety of their infant passengers and could be liable for a £30 fixed penalty or face a £500 fine if the case goes to court.
Mr Fowler said: "You can buy a booster seat for as little as £10. Many shops have trained advisers who can help you choose the right seat for your car. So take your child along and explain why it's such an important buy for the Christmas holidays. It could be the best £10 you ever spend."
