The agreement, which runs up to and including 2009, represents the largest commercial partnership in European rugby history.

RBS's initial three-year agreement ran from 2003 up to and including this year's Championship.

Howard Moody, group director, communications, The Royal Bank of Scotland Group said: ''The RBS 6 Nations is the only major sporting event that sees nations across Europe pit themselves against each other on an annual basis, making it the greatest annual rugby tournament in the world.

''The excitement of the RBS 6 Nations is highlighted by three different winners of the Championship in the first three years of our sponsorship and by extending our association for a further four years we have shown our long-term commitment to the sport and the tournament.''

John Feehan, chief executive of the 6 Nations Committee said: ''The excitement of this year's RBS 6 Nations shows what a superb event this is to be associated with.

''RBS has been a hugely supportive sponsor for the Championship and rugby as a whole and we are thrilled that they have decided to extend their association a further four years.''