There are major problems with six out of seven trampolines, according to the consumer watchdog.
Consumer NZ testing found "serious failures" in three trampolines and only one trampoline passed its critical safety tests.
"The safety failures of six of the seven models were concerning because they could cause injury to kids inside the enclosure: none of the six could stop a child from hitting the structure with a sufficient force to cause head injury, while two had accessible gaps where a child could get their head, limbs or fingers trapped," Consumer NZ said in a press release.
The Springfree trampoline, with soft-edges and a frame and springs beneath its jumping mat, passed all of the impact, structural and entrapments tests.
In 2016, 11,580 trampoline-related injuries were reported to ACC - nearly 4000 more than in 2013.
"Though many injuries are down to how we use trampolines we don't always stick to one-at-a-time supervised bouncing that's no excuse. A poor trampoline design makes it even less safe to use," Consumer NZ head of testing Paul Smith said.
There is no New Zealand safety standard for trampolines, it was retired in 2015, so the tests were modelled on the Australian standard.
"We can see no reason why the Australian standard isn't adopted here," Mr Smith said.