World Rugby chief executive Brett Gosper has urged referees to show more red and yellow cards in an effort to eradicate dangerous tackles in the game.
The number of reported concussions and severe injuries has risen each of the last seven years, according to the Rugby Football Union.
So far this year, four leading players – Dragons centre Adam Hughes, La Rochelle lock Jason Eaton, Ireland back Jack Payne and Leicester back row Dominic Ryan – have been forced to retire as a result of head knocks.
Recent games have seen controversial challenges, including Owen Farrell’s tackle on South Africa’s André Esterhuizen in the dying moments of England’s 12-11 victory a few weeks ago.
The incident was deemed legal as it did not meet the red card threshold in the eyes of the citing commissioner Keith Brown.
Farrell has also escaped a citing commissioner’s warning – a sanction for offences deemed to be between a yellow and red card.
Gosper spoke to the Daily Telegraph earlier in the week regarding necessary changes that he hopes will improve player safety.
“The cards are there to change behaviour,” said Gosper.
“They only continue to be a problem if behaviour does not change. The only way you can get player behaviour to change is to sanction with red cards and actually, we have probably not see enough of it.”
The World Rugby boss went on to say that not enough has been done to persuade players to lower the height of the tackle since the law was altered earlier this year, and he wants referees to take a tougher stance.
In October, European chiefs vowed to continue the crackdown on contact with a player’s head, even though an abundance of red and yellow cards had been issued this season.
Gloucester’s Danny Cipriani was cited and given a three-week ban for a high tackle during his side’s Champions Cup defeat by Munster in October.
Additionally, Toulouse flanker Jerome Kaino and Saracens utility-back Alex Lozowski were given four and five week bans respectively for dangerous tackles.
Gosper concluded by stating: “In many ways we have probably not been hard enough.
"There have probably not been as many yellow cards as we would like, and maybe not even as many red cards as we would like.
“We have not had the behaviour change that we are seeking yet, so we have to continue in that vein.”