Car baby seats should also be used by children until they reached the age of 11, the Consumer Council said yesterday.
Spokesman Matthew Ng said adult seat belts could injure young people in an accident - although it was much safer to use them than no protection at all.
'Use of appropriate child restraint systems in conjunction with the ordinary seat belt provides more effective protection and reduces the risk of possible belt-induced injury during a crash,' he said.
'We would like to urge parents . . . to use appropriate car seats [for their children].' The council refrained from urging the use of such seats in taxis for reasons of practicality.
Transport Department figures show that in the first six months of this year 414 passengers aged 11 or younger were injured in traffic accidents, 128 of them in private cars.
A study commissioned by the US National Highway Traffic Safety Administration found that children aged two to five restrained in adult seatbelts were four times more likely to suffer a head injury than children restrained in a child car seat. Thirteen models of car seats for older children available in Hong Kong all passed independent tests and met European safety standards, Mr Ng said.
Children should use car seats until they weigh more than 36kg and are more than 1.45m tall, the council said.
The top-rated models available in Hong Kong include Maxi Cosi's Oki-Doki, which costs $300, and Bebe Confort's Hispos at $1,720.
'Even the worst-performing seats in the test are better than not using a car seat at all,' Mr Ng said.