Canada rugby legend Jamie Cudmore has defended referee Ben Whitehouse after he allowed scrum-half Morgan Parra to return to the pitch, even though the player was apparently briefly knocked unconscious during Clermont's Champions Cup match against Northampton.

Whitehouse was criticised for a number of decisions in the game but Cudmore, now forwards coach at Top 14 side Oyonnax and founder of the Rugby Safety Network, believes it is unfair to lay all the blame at the referee's door.

Instead, he believes it brings the entire Head Injury Assessment (HIA) process -- which he describes as 'not fit for purpose' -- and clubs' attitude to player welfare into sharp relief.

"Rugby laws say that if a concussion is suspected, a player does not return to play," Cudmore said. "But the professional leagues have put the HIA in place to get around that law.

"Referees have an enormous amount of stress on their shoulders. They're watching things at a million miles an hour. For him to stop the play and have Morgan taken off right away, that was very good. That's what referees need to do. What happens afterwards is out of his hands.

"He would have been well within his rights to say he could not come back on but I think the fact Parra seemed okay after the hit: he was talking to the medic, got up on his own, walked with no problem to the sideline, maybe that swayed his judgement."

Whitehouse's decision received further support on Tuesday when European Professional Club Rugby, the organisers of the Champions Cup and Challenge Cup competitions, published the results of an independent review that ruled that Parra was correctly permitted to return to the field of play.

The EPCR statement highlighted that "an initial Head Injury Assessment (HIA) revealed no loss of consciousness on the part of the player" and that Parra had also passed the first stage of the HIA after leaving the pitch.

"The event involving Parra was referred in the first instance by Alligin Performance to Dr Mike Rossiter, Consultant in Sport and Exercise Medicine, who concluded that the clinical decision-making process was correct in allowing Parra to return to the field of play."

Parra was part of Clermont's side which claimed the Top 14 trophy last season. Jean Catuffe/Getty Images

The referee's mistake, Cudmore said, came before Parra was taken off: "Coming over and saying 'I think he's unconscious', didn't help because everybody on TV heard that and decided Parra's day was done."

But the incident also lays bare the problems with HIAs, Cudmore said: "To me that's where the whole HIA process comes into play. It really needs to be abolished. Sure, Parra came on 10 minutes later -- and he looked fine walking off -- but who really knows?

"We're not going to know more until this week, when he goes and sees the neurologist and they have some time to do some proper testing.

"You don't to learn anything in a hurry-up 10-minute period in a rugby stadium."

Many pundits insisted that Whitehouse should have refused to allow the player to return after his 10 minutes on the sidelines because of his earlier suggestion that the player was knocked out, but Cudmore believes that more responsibility should fall on the shoulders of the medical staff.

"It's too much to put it all on the referee," he added. "He's totally within his rights to say 'he's not coming back on', but he knew the HIA procedure was in place, so he went through each logical step: he saw a player who was injured and he called the medical staff. That's exactly what had to happen.

"When Parra returned, that falls to the medical staff. For me, they're taking a risk with their player.

"I know it was a big game, but I'm scared it's going to come to the point where a player has done his 10 minutes, passed his tests and come back on, and gets another knee in the head -- and comes off again on a stretcher with a blanket over his face."

For Cudmore, the current procedure is being abused by teams and the only solution is to abolish HIAs altogether. "It's not a law. The professional leagues have stepped around the law by putting HIAs in place.

"Teams are using that 10-minute period as 10 minutes off. They're swallowing the pill for 10 minutes -- almost like a yellow card -- knowing that once players have jumped through all the hoops on the sideline they'll go back on, almost regardless of what their scores on the [HIA] test were."

Cudmore is all-too aware of the risks of concussion. He was forced to the brink of retirement shortly before the 2015 Rugby World Cup after suffering a concussion while playing for Clermont in that year's European Champions Cup semifinal against Saracens.

Despite failing an HIA, he was allowed back onto the pitch and lined-up again for the club a fortnight later at the final at Twickenham. He lasted only a few minutes before going off after a tackle with 'second impact syndrome'.

"It was too early to come back," he explained. "The first major contact I made was enough to send me off. I came back and then went off again, and then a third time in the second half. After vomiting, I was still allowed back."

He later told reporters: "It was very scary. The whole month of June I was sitting on my couch. I couldn't watch TV, I couldn't really do anything. I was stuck between the World Cup and retirement.

"I had all kinds of symptoms: headaches, being irritable, tired when you shouldn't be tired, then being really tired and not being able to sleep."