UK doctors have called for a 20 per cent tax on sugary drinks to subsidise fruit and vegetables.

A 20 per cent levy should be imposed on sugary drinks to help battle the obesity epidemic, say UK doctors.

The tax on all non-alcoholic water based beverages with added sugar, including soft drinks, energy drinks, fruit drinks, sports drinks and fruit juice concentrates, could subsidise the sale of fruit and vegetables, they say.

It would reduce the prevalence of obesity in the UK by about 180,000 people, said the new report, Food for Thought, by The British Medical Association.

"While sugar-sweetened drinks are very high in calories they are of limited nutritional value and when people in the UK are already consuming far too much sugar, we are increasingly concerned about how they contribute towards conditions like diabetes," Professor Sheila Hollins said.

"We know from experiences in other countries that taxation on unhealthy food and drinks can improve health outcomes, and the strongest evidence of effectiveness is for a tax on sugar-sweetened beverages.

"The majority of the UK population, particularly low-income households, are not consuming enough fruit and vegetables, so financial measures should also be considered to subsidise their price, which has risen by 30 per cent since 2008."

The report also called for a ban on all marketing of unhealthy food and drink products to children and young people.

Comment has been sought from the Australian Medical Association.

Australian Beverages Council chief executive Geoff Parker said a tax on one type of food or drink should not be promoted as the solution to poor dietary habits.

"Evidence from other countries show that this type of tax does not deliver long-term societal changes," he said.