Video footage describing England as 'Grand Slam Champions 2011', with the Nike swoosh alongside has been leaked on to YouTube.
It features England stars Ben Foden, Toby Flood and Chris Ashton in various action shots, before hailing England's victory.
While England did not win the Grand Slam (which involves defeating every other team in the Six Nations championship), the team did finish top of the table, their only defeat coming against Ireland in Dublin on Saturday.
The leak is likely to cause embarassment at Nike, which had planned to release the video only if England defeated Ireland in the team's final match.
Nike is the official kit supplier to the England rugby team.