Ambulance chiefs admitted an "error" after experienced Australian paramedics declared a man dead following a car crash and left the scene, only for him to be found alive an hour later.

The driver was trapped upside down in the wreckage of a Porsche in a Melbourne suburb and was pronounced dead after being treated on Sunday.

It was only when State Emergency Service volunteers finally began the process of removing what they thought was a corpse that they saw him twitch and discovered a "feeble pulse".

The man was rushed to hospital in a critical condition and is now listed as serious but stable.

Ambulance Victoria chief Greg Sassella said after a preliminary review: "Mistakes do happen. Unfortunately in our work, when a mistake's made, it can have horrible consequences, and in this case that's what's occurred.

"The paramedics have made a decision about whether the patient was alive or not, they've obviously made an error in that," he told reporters.

"So the question is: why did they do it that way in the first place, when we know that they're committed, we know they're genuine, they spend their entire working life helping patients?"

The paramedics were highly experienced and were traumatised by what happened, he added.