LONDON (REUTERS) - Rugby players with brain damage are regularly being sent back on to the field of play because the sport's governing bodies are not taking concussion seriously enough, medical experts said yesterday.

The long-term risks could be higher rates of dementia, major depression and other neuro-degenerative conditions later in life, they added.

They noted that evidence of such problems is already found among American football players who suffer similar rates of knocks to the head.

Barry O'Driscoll, a former International Rugby Board medical advisor who spoke on the sidelines of a Rugby Football Union conference on concussion, said he was in no doubt that injured players were going back into a dangerous environment.

"We are sending concussed players back onto the field - brain-damaged players," he said.

"We know now what's going on in the brain as soon as it is hit. The glucose metabolism, the oxygen uptake, the electrolytes... are all thrown completely out."