Consumer New Zealand says only one trampoline out of five it's tested has met critical safety checks.
The brands were tested based on the Australian standard, which Consumer says is more up-to-date than the kiwi version.
Only the Springfree R54 passed the impact tests, which tested the risk of brain injury from a child's head colliding with the safety padding above the frame.
Consumer Chief Executive Sue Chetwin says the poor results show the voluntary standards for trampolines isn't working.
She says a mandatory standard is necessary if New Zealand is serious about reducing the number of trampoline-related injuries.
