The Portman Group's independent complaints panel came to the decision after its research revealed that more 14- to 17-year-olds than any other age group perceived fcuk Spirit as 'a stylish brand' and 'a brand for people like me'.
It is a landmark ruling because it is the first time the drinks industry watchdog has banned an alcoholic drink that is a brand extension from another sector.
Jean Coussins, chief executive of The Portman Group, said the ruling sends out the "strongest possible message" to drinks companies and brand owners that if their brand appeals to under-18s, they should steer clear of brand extensions into alcohol.
"If owners of other brands which appeal to under-18s are thinking of entering licensing agreements with alcoholic drinks companies, they should forget it," she said.
Fcuk Spirit launched in a range of fruit flavours and a blaze of publicity 18 months ago. However, The Portman Group received just one complaint about the product, in April 2002, from a member of the public concerned that the drink bore the name of a fashion brand bought mainly by teenagers.
A spokesman said the complaints panel took more than a year to reach a decision because it wanted to consider all the facts and give the manufacturer every opportunity to make its case.