Ladders are involved in about 7000 ACC claims for injuries in and around the home each year.
Mr Marston, in his mid-50s, ruptured his calf muscle and severely strained his left ankle in the January accident. He still suffers pain in his ankle and suspects he has arthritis as a result of the fall.
The ladder had been bought on Trade Me and was advertised as meeting European safety standards and having a safe working load of 150kg.
"I can assure you, I'm not 150kg," Mr Marston said yesterday.
"It was the first time I'd used it. I got about three-quarters of the way up. And it snapped in half."
He had been painting in his lounge and fell about 3m to the ground.
"I was, in a perverse way, lucky that I actually kept my balance and landed on my feet.
"There was a lot of solid wooden furniture around, and if I'd gone over and caught the corner with the head, I most probably wouldn't be talking to you."
Ministry of Consumer Affairs principal adviser Martin Rushton said the seller could not provide a valid certificate to show the ladder had passed safety tests.
"We commissioned our own testing by an accredited laboratory and the ladder failed, collapsing like plasticine under a load of 120kg."
The ministry, with the co-operation of Trade Me, identified other buyers of the ladder and notified them of the danger.
The trader is refunding purchasers of the ladder.
Mr Rushton said that as an initial step the ministry was now testing three different ladders bought from separate online traders.
"This will give us a good indication of the level of compliance ... on online trading sites.
"We also want to hear from anyone who has experienced a safety incident that may be due to the structural integrity of the ladder."
He said people should buy ladders that met the Australia and New Zealand standard AS/NZS 1892.1:1996.
"Purchasing ladders that have met safety standards could actually save you money. In this instance the unsafe ladders were more expensive than branded versions sold by major retailers," Mr Rushton said.
But Consumer NZ chief executive Sue Chetwin said that in testing even branded ladders from established retailers had failed to meet safety standards.
Its own testing of stepladders this year found only one of 16 passed all safety tests.
Ms Chetwin said the Australia/New Zealand safety standard should be made compulsory, so that ladders that fail could not be sold.
"It's one you need to be particularly careful about, regardless of whether you're buying online or actually from a bricks and mortar [retailer]."
Trade Me spokesman Paul Ford said the website was "gutted" to hear of Mr Marston's accident, and had assisted the ministry in its actions since.
"The ladder safety standard is voluntary ... but we require traders to comply with the Consumer Guarantees Act and this requires all goods they sell to besafe.
"If you have concerns about the safety of a product, make sure you ask questions of the seller, and report anything to us via the Community Watch button on the site."
