People may think they are avoiding calories when they opt for diet soda, but a new study claims that those who commonly choose diet drinks often compensate for the low calorie content by eating more unhealthy food.

Professor Graham MacGregor, a consultant cardiologist, said the Government should start by slapping a 10 percent tax on all sodas which would gradually rise to 50 percent.

He said that a sugar tax would act as a weapon to force food and drinks manufacturers to make their products less sweet.

Rresearchers linked diet soda consumption to an increased intake of food loaded with cholesterol, fat, sodium and sugar. In other words, if you choose diet drinks, you're more likely to reach for unhealthy snacks as well.

The point of the study was to show that mindful eating — thinking about quality and quantity of your food — matters, and that merely replacing a sugary drink with a diet one may not prevent weight gain.

"They feel they have cut their calorie intake so they can now eat more food," said Professor MacGregor, who practices at Barts and the London and St Georges Hospitals in London.

"They compensate, they feel hungry, they want to eat more. It could be the artificial sweet drinks enhance that. But the facts are, we’re worried about artificial sweeteners in terms of not giving the weight loss they should."

The study suggests switching to diet drinks in an effort to lose weight may not be a good strategy. More research is needed to determine precisely why people who opt for diet drinks consume more unhealthy food, researchers say people should pay attention to both what they eat and what they drink.

Previous studies have already shown that diet soda causes weight gain, so this new finding is just one more reason to quit that diet soda habit for good.

The study is published in the Journal of the Academy of Nutrition and Dietetics.