Six out of seven trampolines failed a critical safety check when tested by Consumer NZ.
Only the Springfree, a soft-edge trampoline with its frame and springs beneath the jumping mat, passed all impact, structural and entrapment tests.
The safety failures of six of the seven models could cause injury to kids inside the enclosure.
None of the six could stop a child from hitting the structure with sufficient force to cause head injury, and two had accessible gaps where a child could get their head, limbs or fingers trapped.
In 2016, 11,580 trampoline-related injuries were reported to ACC, nearly 4000 more than in 2013.
Consumer NZ head of testing Paul Smith said it wasn't the first time they had found safety problems with trampolines. In 2012, a test of five brands turned up a disappointingly similar result. In that test, only the Springfree model passed with no major safety issues.
"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."
All of the trampolines in the test were round, 3m in diameter, and enclosed with a net.
The main safety check was a shock test of the padding or soft-edge system. Consumer NZ assessed if they would adequately protect a child falling head first on to the pads.
They also observed if the pads suffered permanent damage.
The structural integrity of the frame, mat and enclosure were assessed. And finally, Consumer NZ looked for strangulation and hazards or places where fingers or limbs could get trapped, pinched or crushed around the enclosure and the edges of the trampoline.
A Kmart spokeswoman said Kmart took its safety obligations very seriously.
"All our trampolines are tested and standards are measured by an independent, globally recognised laboratory. All of Kmart's trampoline test results indicate compliance with the safety requirements of the Australian Standard for Trampolines - AS4989 -2015.
"We are yet to receive the report from Consumer NZ and look forward to reviewing their findings. Through our testing we feel confident in the safety and performance of our products."
Springfree $1499: This enclosed soft-edge springless trampoline is okay to assemble and easy to use. It passed all safety tests with good structural integrity and no significant user hazards.
Vuly Thunder Medium $1499: This enclosed soft-edge springless trampoline is easy to assemble and use. It failed three major safety tests for structural integrity and pinch or crush hazards.
Jumpflex Classic 100 $689: This enclosed trampoline is easy to assemble and use. But it failed four major safety tests for structural integrity, impact hazards, and pinch and crush points.
Kmart 10ft with enclosure $199: This enclosed trampoline is easy to assemble and use. But it failed four major safety tests for structural integrity, impact hazards, and pinch and crush points.
Playsafe 10ft springless trampoline with enclosure $749: This enclosed springless trampoline is easy to use. But it failed four major safety tests for structural integrity, impact hazards and pinch or crush points. It's difficult to assemble.
Lifespan 10ft hyperjump plus $330: This enclosed trampoline is okay to assemble and use. But it failed five major safety tests for structural integrity, impact hazards, pinch and crush points, and possible head entrapment.
Plum Play Australia Space Zone 10ft Trampoline and Enclosure $349: This enclosed trampoline is easy to use. But it failed five major safety tests for structural integrity, impact hazards, pinch and crush points, and possible head entrapment.