All Black legend Ali Williams has helped save a beached whale - but a whale rescue charity has criticised the method of pulling it by its tail.
In a statement posted online, Project Jonah said the techniques used risked "significant damage" to the whale and put the rescuers themselves in danger.
World Cup winner Williams was travelling by helicopter with ZURU founder Nick Mowbray when the pair spotted the stranded animal on the beach at Mangawhai, north of Auckland, yesterday.
Mowbray told the Herald they were returning from the Bay of Islands when they saw the whale.
Williams is in a relationship with Mowbray's sister, ZURU co-founder Anna Mowbray.
Mowbray said they circled back and landed, telling the Herald the beach was empty when they began their fight to save the animal.
He said they were then joined by local surf lifesavers, who were armed with rope.
Video of the incident, posted to Instagram by Mowbray's partner Jaimee Lupton, shows Williams and Mowbray pulling the whale by its tail to free it from the sand.
At one point the whale gets the better of Williams, slapping the rangy lock with its tail and knocking him into the surf.
Helped by the surf lifesavers, the group then manhandle the whale through the small breakers and back out to sea.
Mowbray told the Herald the whole effort took an hour.
Whale rescue charity Project Jonah earlier shared news of the rescue on their Facebook page, saying they had offered advice to the lifeguards on how to refloat the whale, identifying it as a false killer whale measuring 4-5 metres.
This morning, Project Jonah issued fresh comment after seeing video of the incident, saying the techniques used were dangerous.
"Our advice to Surf Lifesaving New Zealand was for those attending the rescue to stay away from the tail at all costs.
"Unfortunately, the video shows members of the public using rope around the tail and dragging the whale backwards, by the tail, to get it to deeper water.
"This is incredibly dangerous not only for rescuers but can cause significant damage to the whale. While we understand the desire to get the whale back in to deeper water it is important that this is done correctly and safely."
Department of Conservation marine biologist Catherine Peters echoed Project Jonah's concerns.
She said while the group acted on instinct to assist the whale, their actions could have hurt the whale, admitting the incident happened "very quickly".
"Their spinal column is really fragile," Peters said, comparing it to a person taking all of their weight on their lower back.
"By pulling from the tail you're really putting stress on a very sensitive part of the animal and ultimately you could end up effectively disabling that animal."
She said it also posed a "huge risk" to rescuers and any potential injuries to rescuers could lead to future rescue efforts being compromised.