British experts have cast doubt on the safety of an artificial sweetener used in thousands of products including big brand diet soft drinks from Coca-Cola and Pepsi.

Academics at the University of Sussex claim that an EU food watchdog assessment giving a clean bill of health to aspartame, a calorie-free sugar alternative, was seriously flawed.

Professor Erik Millstone, who has been a long-time critic of the additive, argues that there are many scientific studies that raise legitimate safety questions together with circumstantial evidence of neurological harm.

British experts have cast doubt on the safety of an artificial sweetener used in thousands of products including big brand diet soft drinks from Coca-Cola and Pepsi (file photo)

As a result, he is calling for the suspension of authorisation to sell or use aspartame in the EU pending an independent investigation.

He argues that anything from 2-10 per cent of consumers suffer neurological effects, ranging from blurred vision to headaches and, in a small number of worst cases, seizures.

'I have had about 250 people come to me saying they think aspartame caused a problem,' he said.

'I would describe it as strong circumstantial evidence that they have had neurological symptoms and have eventually come to the conclusion aspartame was responsible.'

Prof Millstone has previously been criticised by the makers of aspartame, who have questioned his expertise, accused him of ignoring scientific evidence and suggested he is obsessed.

Aspartame is roughly 200 times sweeter than table sugar and has been used as a calorie-free alternative in more than 6,000 consumer foods and drinks, including Diet Coke, Coke Zero and Pepsi Max.

Aspartame is roughly 200 times sweeter than table sugar and has been used as a calorie-free alternative in more than 6,000 consumer foods and drinks, including Diet Coke, Coke Zero and Pepsi Max

It is sold worldwide under the trade names NutraSweet, Candarel and Equal.

A research paper by Prof Millstone and Dr Elisabeth Dawson details what it says are serious flaws in the way the European Food Safety Authority (EFSA) assessed research on aspartame in 2013 and declared it safe.

The academics argue that – since 1974 – scientists have warned of the risks of brain damage, liver and lung cancer, and brain lesions.

They also point to an EU-funded project published in 2010, which found that pregnant women who consume a high number of fizzy drinks containing artificial sweeteners appeared to be at greater risk of having a premature baby.

The study, published in the Archives of Public Health, says an EFSA panel discounted the results of 73 studies that indicated aspartame could be harmful, but treated 84 per cent of studies providing no evidence of harm as useful and reliable.

Gavin Partington, director-general at the British Soft Drinks Association, said: 'The author of this study is a committed critic of aspartame, despite the substantial body of scientific research that undermines his claims.

According to all leading health authorities in the world, as well as Cancer Research UK and Diabetes UK, low- and no-calorie sweeteners are safe.

'A study on behalf of the UK Food Standards Agency found no negative health links related to consumption of aspartame.'

The EFSA stood by its decision to authorise aspartame. It said: 'EFSA's opinion represents one of the most comprehensive risk assessments of aspartame undertaken.

After a review of all available scientific data and consumption information, EFSA concluded that aspartame [is] safe for human consumption at current levels of exposure.'

The International Sweeteners Association, which speaks for manufacturers, said: 'The EFSA scientific opinion on aspartame concluded that aspartame is not a safety concern.'