The heir to the throne has always prided himself on his alternative views, establishing himself as something of a royal iconoclast who gives voice to public fears over GM foods and nanotechnology, while pioneering a simpler vision of society based on championing organic agriculture, local produce and traditional architecture.

But this time, Prince Charles's embrace of the alternative has led to him being accused of peddling "outright quackery".

Britain's leading academic expert on complementary medicine has warned that the Duchy Herbals Detox Tincture - a food supplement, which combines artichoke and dandelion and promises to rid the body of toxins while aiding digestion - is based on notions which are "implausible, unproven and dangerous".

The heir to the throne, says Edzard Ernst, professor of complementary medicine at Exeter University, is deliberately ignoring science, preferring to rely on "make-believe and superstition".

Ernst said: "Prince Charles contributes to the ill-health of the nation by pretending we can all over-indulge, then take his tincture and be fine again. Under the banner of holistic and integrative healthcare he thus promotes a 'quick fix' and outright quackery.

"It is implied that we can all over-indulge a bit and put it all right with detox tincture. It is encouragement of an unhealthy lifestyle. All the people I have talked to see it in the sense that you can get rid of your own bad habits in that way."

Even if detox potions did not encourage overindulgence, Ernst says it would be wrong to sell them during the recession - because they simply don't work.

"Nothing would be easier than to demonstrate that detox products work," Ernst said. "All one needed to do is to take a few blood samples from volunteers and test whether this or that toxin is eliminated from the body faster than normal. But where are the studies that demonstrate efficacy? They do not exist, and the reason is simple: these products have no real detoxification effects."

Ernst, whose career is devoted to accumulating and assessing scientific evidence to prove or disprove the worth of alternative therapies, was reviewing the evidence on the increasing number of products sold as detoxification agents at the time that the Duchy launched its own. The Prince's products are on sale in Boots and Waitrose.

"It's one of those big subjects like anti-ageing and slimming remedies where there is so much quackery," he says. "I thought somebody has to make a sober analysis." The Prince also faces the prospect of official censure, after the Advertising Standards Authority confirmed yesterday it was investigating the claims made on behalf of the detox tincture, following a separate complaint.

Other scientists share Ernst's scepticism on detox. In January, a group called the Voice of Young Science, part of the charity Sense About Science, produced a study claiming consumers were being misled.

While manufacturers used the word detox to "promote everything from foot patches to hair straighteners", they were unable to provide reliable evidence or consistent explanations of what the detox process means, said the scientists.

The study followed a denunciation from the British Dietetic Association, which represents 6,000 UK dieticians, which said there was no "potion or lotion" to "magically" rid the body of chemicals. They dismissed the idea that dangerous toxins build up in the body, saying the body was more than capable of cleaning itself.

Andrew Baker, chief executive of Duchy Originals, said the tincture was a legitimate food supplement. "It is a natural aid to digestion and supports the body's natural elimination processes. It is not - and has never been described as - a medicine, remedy or cure for any disease.

"Duchy Herbals Detox Tincture contains globe artichoke and dandelion, which both have a long history of traditional use for aiding digestion. There is no 'quackery', no 'make believe', no 'superstition' in any of the Duchy Originals herbal tinctures. We find it unfortunate that Professor Ernst should chase sensationalist headlines in this way rather than concentrating on accuracy and objectivity."

Ernst counters that there is some evidence that artichoke can lower cholesterol, but statins do a better job, and that there is no proof dandelions do any good at all.

Ernst and the Prince have crossed swords before. Ernst believes he nearly lost his job in 2005, after Clarence House wrote to Exeter University alleging he had broken a confidentiality agreement. Ernst had signed the agreement before giving an interview for a report commissioned by the Prince's Foundation for Integrated Medicine, which was investigating whether alternative therapies such as acupuncture would save the NHS money.

When a newspaper approached him for comments on a draft of the report, which suggested the NHS could save up to £3.5 billion if it embraced alternative therapies, Ernst said the initial findings were "outrageous and deeply flawed". A subsequent complaint by Clarence House embroiled Ernst in a year of disciplinary hearings. He was later cleared of all wrongdoing.

Tinctures on sale

Duchy Herbals Echina-Relief Tincture

Described on its website as intended to relieve "the symptoms of the common cold and influenza-type infections". Echinacea "is believed to have been used first ... by Native American people", it says. Ernst does not object, saying there is real evidence of the efficacy of echinacea against colds.

Duchy Herbals Hyperi-Lift Tincture

Designed to lift "slightly low mood and mild anxiety", the website says. It contains St John's wort, which has performed creditably in trials involving mild depression (although not anxiety). People should tell their doctor if they use this and conventional drugs, for fear of interactions.

Duchy Herbals Detox Tincture

Described as helping "eliminate toxins and aid digestion", it is made from extracts of dandelion and artichoke, says the website. Ernst says the product will do nothing for consumers and the concept of detox is implausible and unproven.