A Bay of Plenty support agency says the upcoming closure of Plunket's car seat services will be particularly hard on low-income families.
Plunket is phasing out its rental and retail car seat services after more than 30 years in the business.
Plunket chief operating officer Andrea McLeod said it planned to stop the services in the next 12 to 18 months because fewer people were using them.
Glynette Gainfort, a co-ordinator of Tauranga's Strengthening Families service, said the closure would leave a gap in the community.
"The removal of a service that's cheap and easy to access is going to be problematic for families, particularly ones on low incomes, as many of the families we see are," she said.
"I don't know what other hire services are available but there's definitely families who would struggle to buy car seats if that's the only option."
Ms Gainfort expected families would try and buy car seats second hand or get them off friends.
"But that doesn't mean they shouldn't still be checking they're up to safety standards and not past their expiry date."
The cost of upgrading car seats possibly contributed to some children not being in correct restraints, she said.
The number of Plunket sites offering car seats declined from 283 at its peak in the 1980s, to 72 today. Despite efforts to make the service sustainable, sites across the country had been closing as they could no longer afford to operate. The majority of the sites only operate part-time, a few hours a day, several times a week.
"The decline indicates families' needs have changed," Ms McLeod said.
When Plunket started offering car seat and capsule hire in 1981, just 20 per cent of children were buckled in. That number had risen to 93 per cent.
However, recently released data by Safekids Aotearoa showed car crashes were still a major cause of children's injuries and deaths.
Between 2006 and 2010, nine Bay of Plenty children died in car crashes.
This was the leading cause of children's deaths in the region and third highest number of children to die as a result of car crashes in the country.
Nationwide, car crashes were the second most common cause of children's deaths - second only to suffocation. Safekids Aotearoa director Ann Weaver said the number of car crash deaths was far too high.
"In most cases the deaths were totally preventable," she said. "Most parents use car seats but a lot aren't installed correctly.
"Most countries only have one standard for car seats, but in New Zealand there's four - American, European, Australia/New Zealand and Japanese.
"We also import cars from a number of different countries so getting the right car seat for a car can be difficult."
Safekids believed children should have to be restrained until they are 148cm tall, she said. Seatbelts are designed for children 150cm and over.