World Rugby has issued a crackdown on dangerous play involving the head by reminding referees to punish any severe examples with a red card.

On the eve of England and Scotland’s opening autumn internationals and a week after Wales and Ireland opened their campaigns, the sport’s global governing body has ordered its officials to be “especially vigilant in this area”.

The edict has demanded a strict approach to tackles, charges, strikes or kicks that make contact above the shoulder line and calls for firm sanctions for offenders.

"World Rugby's number-one priority is player welfare and the laws of the game clearly state that the necks and heads of players are sacrosanct," World Rugby match officials selection committee chairman Anthony Buchanan said. "When it comes to foul play, the game is cleaner now than ever before but referees must constantly be alert to head-high hits.

“By taking this strong approach, we are saying to players that tackling an opponent above the shoulder line will not go unpunished. “In addition, while striking or kicking an opponent is never acceptable, it is a more serious offence when it involves contact with the head or neck.

“Even ball-carriers must be careful that they fend off tacklers legally and do not strike opponents with forearms or elbows. “While this specific directive is going out to match officials at the elite international grade, we are reminding all unions and referee societies at every level of rugby to take note and strictly enforce current law in this important area.”

Concussion is the most common injury suffered by rugby players and numerous studies have suggested the condition can cause lasting and serious effects.