World Rugby has faced strong condemnation from all elements of the game for its admission that referee Craig Joubert blundered in awarding Australia their decisive penalty against Scotland.

A distinguished former player, a national coach and the sport's most experienced referee have each savaged the governing body for stating Joubert should have awarded a scum instead of a penalty in the nail-biting closing moments of Sunday's World Cup quarter-final.

Bernard Foley kicked the three points to snatch a 35-34 victory at Twickenham that robbed Scotland of a place in the last four, but the call for accidental off-side was incorrect.

Wallabies great David Campese insists the World Rugby official who signed off the public rebuke of Joubert "should be shot", Australia coach Michael Cheika describes his treatment as "so unfair" and retired referee Jonathan Kaplan now fears for the image for the game.

A backlash has formed following the vilification of Joubert - with former Scotland internationals Gavin Hastings and Andy Nicol the culprits in chief - and Campese has added his voice to growing chorus of support for the South African.

"I have been in games where referees have made real blunders, but whoever put that statement out saying the referee got it wrong should be shot. Now you're actually saying the referees are bad," said Campese.

"One of the biggest problems in world rugby is trying to get referees, and if they're going to cop abuse every game - meaning there will be no referees - then we haven't got a game.

"I know they make mistakes, but you have to live with them. I would hate to be a referee. There is so much happening. They are human and they do make mistakes."

Pointing the finger of blame at Joubert is an unusual but not unprecedented step by World Cup and Cheika - speaking on the subject for a third successive day - believes the official has been let down.

"I genuinely feel for Craig Joubert. It's so unfair. No other referee has had this stuff put out there like that and he's a very good referee," Cheika said.

"I would have liked my mates to back me up a little more on the odd occasion, if you know what I mean. I feel for him. We talk about having the right principles in the game and all of that...

"Genuinely I have never seen that before. I am not sure why that decision had to be publicly reviewed and put out there.

"I really hope his fellow referees stand by him because - well, the fact I'm not allowed to say much about it says it all."

World Rugby said in a statement that having reviewed the incident, the "appropriate decision was a scrum to Australia for the original knock-on" and not a penalty.

Scotland were outstanding as they fought back to establish a 34-32 lead in one of the World Cup's greatest knockout matches, only to be robbed of a famous victory by Joubert's pivotal late call that helped the Wallabies creep ahead with 43 seconds remaining.

Joubert will play no further part in the competition after being overlooked for this weekend's semi-finals.

Kaplan, rugby's most experience international referee and a veteran of four World Cups who retired two years, has leapt to the defence of his compatriot.

"I'm just wondering whether this is a good look for World Rugby to be criticising their own assets," Kaplan told BBC Radio 5 live.

"Craig is definitely in the top four referees in the world and that's why he has been chosen to do the quarter-finals onwards.

"If World Rugby were going to come out and clarify the decision, there's a lot more they could have shared with the public."