He said the Government should not have done a U-turn on its regulations - and should stick to its guns.
"In the US, we got to that point of cooking well-done hamburgers about 25 years ago after a really terrible E. coli outbreak linked to undercooked hamburgers - the Jack in the Box E. coli outbreak - 700 people sick, four children died, about 60 children developed acute kidney failure and required dialysis."
After that, nationwide cooking temperatures were changed to ensure hamburger patties were cooked to well-done, he said.
"Over time, we've seen those outbreaks move to close to zero. So those regulations work. I frankly was a little surprised that New Zealand hadn't implemented that like 20 years ago. They're a little behind the times."
Marler said he thinks people just don't understand how deadly this bacteria could be.
"If it gets in the meat and you don't cook it out, it could sicken or kill your child."
When asked if he would eat a medium-rare burger cooked at a downtown Auckland restaurant, he said, abruptly, "No. Not at all."
"I'd like to see a little bit more of the data behind about how safe the product is. But I would stay away from a medium hamburger. I'd certainly keep my kids away from it."