Dr Willie Stewart, consultant neuropathologist at the Southern General Hospital in Glasgow, said he was “sickened” that Welsh star George North resumed playing after twice being injured during the loss to England on Friday.
North underwent mandatory concussion assessment after an accidental boot in the head in the first half, but returned to the field and later clashed heads with a team-mate.
Millions watching on TV saw North fall, apparently unconscious, but the incident was not seen by team medics and the 22-year-old wing carried on.
Dr Stewart, a world authority on concussion in sport, who has identified a link between early-onset dementia and concussion in rugby, said: “I was incredibly disappointed.
“It illustrated to me in one sense how far we’ve come with concussion in sport, but how far we’ve still got to go.”