We are very conscious of the kind of negative publicity that would be generated if exaggerated claims were made about tea

Bill Gorman, Tea Council

A rival tea firm complained to the Advertising Standards Authority, which ruled against the advert.

It found that as the health benefits of tea were not proven, the adds were "misleading".

It also ruled that as many of the benefits were from the milk, the advertisers had "exaggerated the health benefits".

Cautious claims

The advertisers - a Sri Lankan firm called Ceylon Tea Services - said they had simply used information provided by the Tea Council, a UK based group which promotes the industry.

However, Bill Gorman, the director of the Tea Council, said this information had been misrepresented.

He told BBC News Online: "There is a great deal of evidence that tea has beneficial effects on health - but as an industry we have always been very cautious about saying this.

"We are very conscious of the kind of negative publicity that would be generated if exaggerated claims were made about tea.

"However, this is a very competitive marketplace."

The health benefits of tea are not fully established, but it is thought that antioxidant chemicals called flavanoids may be beneficial, perhaps by improving the function of the walls of blood vessels.