The 'cannonball' tackle is now officially disallowed after the NRL issued clubs with new guidelines which will protect players from this type of tackle.

Also known as a 'kneecapper' the tackler charges at his opponent's legs while he is being held up by the tackler's teammate. 

The new guidelines will take effect from this weekend's NRL and Toyota Cup matches.

NRL referees' coach Stuart Raper said the guidelines would be welcomed by players and fans.

He said the measures were not designed to stop a player tackling around the legs, but to give referees the option to take action when a potentially dangerous situation arose.

He added that player safety was paramount.