The Duchy Herbals Detox Tincture claims to be able to detox the body and aid digestion when one or two drops are added to a glass of water. The product, which contains dandelion and artichoke, costs £10.
In addition to the ASA investigation, a senior expert on complementary medicine has attacked it claiming the product is the result of "make believe" and "superstition".
Professor Edzard Ernst of Exeter University said the science behind the Duchy Herbals Detox Tincture was "implausible, unproven and dangerous". He pointed out the absence of any scientific study to prove the tincture actually worked.
Prince Charles has frequently spoke in favour of the benefits of alternative medicine, such as acupuncture, and organic farming.
Duchy Originals chief executive Andrew Baker said the tincture was a natural aid to digestion and was not supposed to be a medicine. Dandelion and artichoke "have a long history" of aiding digestion.
There are three different Duchy Herbals Tinctures available. The other two are Echina-Relief Tincture, an echinacea product, and Hyperi-Lift Tincture which is designed to combat depression and contains St John's Wort.
Prince Charles
Prince Charles' herbal product investigated by the ASA
LONDON - Prince Charles' Duchy Herbals brand is being investigated by the Advertising Standards Authority (ASA) over claims made about its Detox Tincture product.