Also unsubstantiated, ruled the ASA, was the claim that the drink would "rehydrate and replenish energy faster than any other type of drink".

As the drink was produced under licence it was the licensee that made the contentious claims and not Umbro

Umbro

The ASA found no evidence to show the drink outperformed others.

Sportswear giant Umbro, the official kit sponsor of the England football team, last year lent its name to the new line of "hypotonic" energy drinks made under licence by Edinburgh-based GoPack Superdrinks Ltd.

The drink soon became the staple pre- and post-match replenishing fluid for footballers at more than 100 top clubs including Celtic, Nottingham Forest and Crystal Palace.

It even threatened to topple market leader Lucozade Sport, the official beverage of the Premiership, from its position at the top of the energy drink chart.

But GoPack has now been told that it can no longer use claims about the drink, including that it was created by a "respected sports nutritionist".

While claiming it was made to a proven scientific formula, the only evidence it gave to support this was an article written by the person responsible for the formula.

�2m sales

The ASA said it launched an investigation after receiving a complaint from SmithKline Beecham, which makes Lucozade Sport.

Umbro said on Tuesday it was up to GoPack to substantiate any claims about the drink.

"As the drink was produced under licence it was the licensee that made the contentious claims and not Umbro," said a spokesman.

GoPack said it had withdrawn the drinks from sale on 31 December after chalking up sales of more than �2m.

Company director Bob Jameson said it had no plans to resume production.