Young people could end up behind the driving wheel barely five years after being allowed out of car booster seats, if child safety advocates have their way.

As the Government prepares to include the issue of child car restraints in a discussion paper on new road safety measures, the Paediatric Society says youngsters should be kept in booster seats until they turn at least 10, to prevent horrific abdominal or neck injuries.

That organisation of child health experts is taking a different tack to the Plunket Society, which believes height rather than age should be the determining factor.

But both societies agree existing legislation allowing children to swap their booster seats for adult safety belts as soon as they turn 5 is leaving New Zealand behind other countries.

British children shorter than 135cm have to stay in booster seats until they turn 12, and many European countries have set 1.5m as the minimum height for graduating to adult belts.

Even Australia, which until now has been trailing the field by requiring children to wear special restraints only until they turn 1, is about to leapfrog New Zealand by raising the age to 7 from the end of this year.

Plunket passed a resolution yesterday at its biennial conference seeking a clearer law for the use of booster seats for children aged 5 and over.

"What we really want to stop seeing is 5-year-olds just using vehicle safety belts," society national child safety adviser Sue Campbell said last night. "Nothing sits right and they are susceptible to being ejected out of vehicles in some crashes, or receiving horrific internal injuries from incorrectly positioned belts."

But Paediatric Society president Rosemary Marks said stipulating a minimum height would cause enforcement issues, and setting a required age at 10 or 11 would be a more practical and reasonable solution, notwithstanding juvenile protests.

She said the European Union had set 12 as the ideal age, at which point most children were taller than the 148cm which researchers agreed was the minimum height at which adult seat belts should be worn.

A spokeswoman for Transport Minister Steven Joyce said the issue of child restraints would be included in public discussions towards developing a strategy for improving road safety from now until 2020.