Previous research has shown that tea contains high levels of compounds that combat the absorption of fat.

However, a new research led by an Indian scientist has found that this fat-fighting ability will be neutralised if milk is added to it.

The compounds, called theaflavins and thearubigins, stopped the pounds from piling on when given to rats on a high-fat diet.

But proteins in cows' milk neutralise this fat-fighting ability.

Devajit Borthakur, of the Tea Research Association in India, told The Sunday Telegraph that the chemistry between the milk proteins and the fat-fighting compounds means “we don't get the health benefit from these compounds.”

The finding is bad news for Britons, who add milk to 98% of the 165million cups of tea they make a day.

“From a public health perspective, tea is rich in antioxidants and may be an important contributor to an individual's overall antioxidant status,” said researcher Lisa Ryan of Oxford Brookes University.

“The addition of milk, however, may lower the total antioxidant capacity of tea; however this effect is much greater with skimmed milk compared to whole milk,” she added.

The research is published in the journal Nutrition this month.