"When a seatbelt is the wrong size it can be quite dangerous. My kids are quite short and they'd get clothes-lined if we were in an accident," she said.
Associate Minister of Transport and Tauranga MP Simon Bridges yesterday announced the law change, which will increase the mandatory use of restraints in vehicles for children.
Under the new rule, children up to 7 years must be in an appropriate child restraint, and those aged between 7 and 8 will be required to use a child restraint if one is available.
"International and local research shows that in the event of a crash, young school-age passengers are at considerable risk if they are only restrained by an adult seatbelt," said Mr Bridges.
"Injury risk can be significantly reduced by having child passengers use age-appropriate restraints, such as booster seats. Extending the mandatory restraint requirements is an important step up."
The law change will bring New Zealand into alignment with other countries, including Australia.
"We have the lowest age for child restraints (5) in the OECD, which is of all the developed countries and consequently we have the highest number of child injuries. Research shows young school-aged children are at a considerable risk in an accident using an adult seatbelt.
"They can cause serious problems in their abdomen, spine, neck and their head, which can lead on to more serious disabilities for life," Mr Bridges said.
Bay of Plenty District Health Board medical officer of health, Jim Miller said the DHB supported any initiative that would improve child safety in vehicles.
Dr Miller said smaller children should continue to use booster seats even if they were over 7.
Plunket manager for car seat services for the Bay of Plenty/Lakes districts, Sandy Waugh, said she believed it was about time the law changed. "The last time we had an update in the law was in 1994, so that's too long.
"The roads in New Zealand are twisty and turny and accidents are more prolific [than in other parts of the world] and very often children are involved."
Mrs Waugh has 11 grandchildren, six of whom are over the age of 5.
"And they still have booster seats and I wouldn't have it any other way," she said.
The new law is expected to be in place within 12 months.
Mr Bridges said a period of consultation and education would take place to make sure practical issues with the new rules were addressed.
School buses will not be affected by the change and young children will continue to travel on buses without seatbelts or booster seats. When the new rules come into effect, people who do not comply could face an infringement fee of $150 or a fine anywhere up to $1000, Mr Bridges said.
The Ministry of Social Development will be able to help people who cannot afford booster seats.