New Zealand coroner raises alarm over 'perilous' collision sport
"Runit" competitors line up 20 metres (65 feet) apart and run directly at each other, with the winner being the person who "dominates the collision".
Coroner Bruce Hesketh issued the warning as a separate comment in his report into a club player who died after being tackled in a traditional rugby league game.
The Australian-based Runit Championship League set up a base in New Zealand this year.
It offers a NZ$20,000 (US$12,000) prize to winners of regional competitions and NZ$200,000 to the overall winner of the tournament.
Fuelled by social media, unsanctioned splinter events have been held in both Australia and New Zealand.
In May, 19-year-old Ryan Satterthwaite died in New Zealand after suffering a serious head injury during one such event.
Hesketh, who is not looking into the teenager's death, said he was concerned about the Runit events.
"The competition has all the hallmarks of perilous activity that makes no attempt to mitigate head injury," he said.
"There appears to be no governing body, the activity is not regulated and has no written publicly accessible rules of participation.
"Neither is there any information to players around the signs and dangers of concussion or concussion management."
Hesketh said the goal in rugby union or rugby league is to avoid tackles, whereas the goal in Runit competition is the opposite.
"Furthermore, all the applicable team sporting bodies involved have invested heavily in concussion awareness, prevention, identity and management," Hesketh said.
Runit events "should not be recognised as an official sport", he said.
The Runit Championship League touts itself as the "home of collisions".
After Satterthwaite's death, New Zealand police warned people to be wary of the "significant" injury risks.
In the Runit Championship League's first event in Auckland in May, two people were knocked out, and one man ended up having seizures after suffering a head injury.
The collision that led to the seizures was greeted with loud cheers from a crowd of more than 1,000 people.
The league organisers had planned to host the final event in Auckland but moved it to Dubai after calls for it to be banned in New Zealand.
The league is flying all competitors to the June 28 final at the Agenda Arena in Dubai.