A leading concussion expert says rugby's concussion tests are flawed and brain damaged players are being returned to play.
The comment was made by the former International Rugby Board medical advisor and Irish international, Dr Barry O'Driscoll, in another open letter to World Rugby
O'Driscoll has been a strong opponent of the various methods introduced to try and curb head injuries as well as how players can be allowed back onto the field after passing cognitive tests.
His latest letter comes after the Highlanders forward Josh Hohneck returned to the field during his side's win over the Cruasaders despite apparently being knocked unconcious.
O'Driscoll says the concussion test doesn't work, although the Highlanders coach Jamie Joseph says he's satisfied and has included Hohneck in his side for this week's match against the Blues.
O'Driscoll says the test is not used by any other sport and has no precedent.
"The outcome is that more brain damaged players are being returned to play," he said.
"The sickening incident with Josh Hohneck this weekend proves this."
Last week, the former all Black prop Ben Afeaki retired from rugby due to the danger of suffering another concussion.