An artificial sweetener used in thousands of products including diet fizzy drinks, ice cream and chewing gum has been ruled a “possible” cause of cancer by the World Health Organisation (WHO).

But a panel of experts has said the sugar substitute aspartame is safe in limited quantities.

In a report released late on Thursday, the WHO’s International Agency for Research on Cancer (IARC) classified aspartame as “possibly carcinogenic to humans”.

The IARC has two more serious categories, “probably carcinogenic to humans” and “carcinogenic to humans”.

We're not advising consumers to stop consuming (aspartame) altogether. We're just advising a bit of moderation

The Food and Agricultural Organisation’s Joint Expert Committee on Food Additives, who carried out a complementary study, retained its advice that it is safe for a person to drink 0-40mg per kilogram of body weight each day.

The WHO said a person weighing 70kg would need to consume more than between nine and 14 cans of diet soft drink per day to exceed the daily guideline.

Dr Francesco Branca, director of the WHO’s department of nutrition and food safety, said: “Cancer is one of the leading causes of death globally. Every year, one in six people die from cancer. Science is continuously expanding to assess the possible initiating or facilitating factors of cancer, in the hope of reducing these numbers and the human toll.

“The assessments of aspartame have indicated that, while safety is not a major concern at the doses which are commonly used, potential effects have been described that need to be investigated by more and better studies.

“We’re not advising consumers to stop consuming (aspartame) altogether. We’re just advising a bit of moderation.”

Widely used as an artificial sweetener since the 1980s, aspartame is used in diet drinks, chewing gum, gelatine, ice cream, dairy products such as yoghurt, breakfast cereal, toothpaste and medications such as cough drops and chewable vitamins.

Both studies cited “limited evidence” and called for more research into the issue.

The WHO said it and the IARC would continue to monitor evidence and encourage independent research groups.

Harriet Burt, senior policy and international projects officer for World Action on Salt, Sugar & Health based at Queen Mary University of London, said the report emphasised the need for a new approach by food and drink manufacturers.

She said: “This new report from the WHO shows that companies need to reduce the overall sweetness of their products rather than relying so much on sweeteners.

“When done correctly, reformulation can gradually remove excess sugars, salt and saturated fat from foods to improve their overall healthiness without the need for replacement ingredients such as non-sugar sweeteners.”

She continued: “Worryingly, sugar consumption in the UK is still double the recommended levels due to a food system that promotes overconsumption of excessively sweet products high in salt and saturated fat. This is why reducing sugar consumption should remain a priority.

“Based on recent WHO reports, it is clear that the UK government urgently needs a comprehensive strategy to reduce not just sugar but overall product sweetness, including the use of non-sugar sweeteners like aspartame.”