London Irish centre Steve Shingler has failed in his appeal against the four-week suspension he received for being sent off against Cardiff Blues.
The independent appeal committee ruled that there were no grounds to alter the original decision.
Shingler, 20, was sent off for a 'spear' tackle on Dafydd Hewitt.
The Welshman was initially given an eight-week ban but that was reduced to four weeks because of his good disciplinary record.
Shingler will be available again from 18 December.