World Rugby chief Brett Gosper calls for more cards to stop dangerous tackles

World Rugby chief executive Brett Gosper has called for referees to brandish more red and yellow cards in an effort to eradicate the dangerous tackles he believes are blighting the game.

The autumn internationals have been marked by a series of controversial challenges by high-profile players, including England co-captain Owen Farrell, which went unpunished with a card.

The number of reported concussions has risen in each of the last seven years, according to the latest RFU data, and so far this year four leading players - Ireland back Jared Payne, Dragons centre Adam Hughes, La Rochelle lock Jason Eaton and Leicester back row Dominic Ryan - have been forced to retire as a result of head knocks.

Gosper says not enough has been done to persuade players to lower the height of the tackle since the law was changed earlier this year and wants referees to take a tougher stance.

"The cards are there to change behaviour," Gosper told the Daily Telegraph. "They only continue to be a problem if behaviour does not change.

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"The only way you can get player behaviour to change is to sanction with red cards and actually, we have probably not seen enough of it.

"I would say 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."