Child safety group Kidsafe says too many children are unsafe in their family cars, and is warning parents to get their car seats checked.

The not-for-profit organisation's mission is to support parents and carers to prevent unintentional injuries to children.

"It's 85 to 90 per cent," Kidsafe NSW Executive Officer Christine Erskine said.

That data comes from research done by Neuroscience Australia.

'Children are not travelling as safely as they should'

Kidsafe NSW regularly conducts fitting days for hundreds of parents and carers.

"We had one in June where we had something like 350 seats checked and 90 per cent had one or more problems," Ms Erskine said.

Fitting days happen all over the country with comparable figures.

"It's a high rate of incorrectly installed seats or incorrectly installed children, and consequently children not travelling as safely as they should," she said.

"Car seats are complicated – people are moving them a lot, parents might put them in and take them out, grandparents might put them in and take them out."

People tend not to read instructions or are in a hurry and fail to check the child or the car seat is installed properly, she added.

"They're also not aware that you can go onto YouTube and watch how to put them in," Ms Erskine said.

"Most people don't actually go to an authorised fitter."

Safety standards for car seats

There are safety standards for both the design of the child restraint and the installation of the seats.

Under the Australian Consumer Law, there is a mandatory safety standard for child restraint systems for use in motor vehicles.

The safety standard covers a number of key requirements including installation instructions, labelling and packaging.

Parents and carers, by law, need to ensure they meet these standards.

"The ACCC advises consumers to purchase child restraints from reputable suppliers that can show the product meets the Australian mandatory safety standard," an ACCC spokesperson said.

The ACCC's 'Your First Steps' and Product Safety Australia websites have important information for parents and carers on choosing a car seat and how to use and install it safely.

The use of child restraint systems is regulated by state and territory road transport authorities, while user requirements and are enforced by the police.

There are significant fines for families that incorrectly install child restraints.

The key problem is that there's nothing stopping a parent or carer from incorrectly installing a child restraint on their own.

How to install a car seat correctly

Babysafe is one of a number of Authorised Restraint Fitting station in Sydney.

Babysafe Owner Rob Mesite said he spends much of his week re-adjusting unsafe child restraints that have been incorrectly installed by owners or unauthorised businesses.

"[Frequently] the vehicle seat belt that is securing the child restraint to the vehicle is unbuckled," he said.

"This is a very common occurrence – I have seen four since Saturday."

Another common problem is people not knowing how to loosen and tighten the harness.

"The harnesses should be loosened and tightened every time we take the child in and out of the child restraint," he explained.

Christine Erskine wants to send the message that far too many Australian children are currently not travelling safely in their family motor vehicles.

"This is a fairly substantial product, it has major consequences if it's not installed properly, so how can we help you?" she said.

"It's very hard to actually legislate compliance because you then have to have checks."

The next best option, she said, is to get the message out that parents and carers need to make sure their child seats are installed correctly.