Susan Jebb, head of diet and obesity research at the Medical Research Council's Human Nutrition Research unit in Cambridge, told the Sunday Times she had herself stopped drinking orange juice and advised others to do so, or at least drink it diluted. The paper quoted her as saying she would support a wider tax on sugar-heavy drinks.

Jebb works closely with the government on diet and obesity issues, and leads the government's so-called health responsibility deal, which oversees voluntary pledges by the food and drink industry to improve public health.

Jebb told the Sunday Times she did not see juice as a healthy option: "I would support taking it out of the five-a-day guidance," she said. "Fruit juice isn't the same as intact fruit and it has got as much sugar as many classical sugar drinks. It is also absorbed very fast so by the time it gets to your stomach your body doesn't know whether it's Coca-Cola or orange juice, frankly.

"I have to say it is a relatively easy thing to give up. Swap it and have a piece of real fruit. If you are going to drink it, you should dilute it."

The paper said Jebb, who is also professor of diet and population health at the University of Oxford, backs a tax on sugary drinks but does not think ministers would support this.

Her comments follow a similar warning in September by two US scientists, Barry Popkin and George Bray, who exposed the health risks of fructose corn syrup in soft drinks in 2004.

Popkin, a professor of nutrition at the University of North Carolina, told the Guardian that fruit juices and fruit smoothies were "the new danger".

He said: "Think of eating one orange or two and getting filled. Now think of drinking a smoothie with six oranges and two hours later it does not affect how much you eat. The entire literature shows that we feel full from drinking beverages like smoothies but it does not affect our overall food intake, whereas eating an orange does. So pulped-up smoothies do nothing good for us but do give us the same amount of sugar as four to six oranges or a large coke. It is deceiving."