Once substituted, players cannot be replaced, but a player who leaves the pitch for a blood injury can return to the field of play later on.

It is this rule that the players are allegedly breaking both in the club game and at international level, using it for tactical rather than genuine injury reasons.

Best told the Sunday Times: "They (blood capsules) are in common use in the Premiership, and I believe that they are the same as you'd find on the set of any film with stunt scenes.

Wasps' director of rugby Nigel Melville agreed with Best's comments.

"I have heard about the use of fake blood capsules and my view is that match officials are not very vigilant in checking blood injuries," he said.

"The fourth official should check them, but at present the touchline procedure is slack."

Former England hooker Richard Cockerill revealed that during one match stitches in an existing cut on his finger were opened up by the England back-room staff.

He claimed the idea was "to take me off for 'blood' just in case it was necessary to bring me back on."