The Medicines Control Agency (MCA) imposed the immediate ban on Aristolochia, on the advice of the Committee on Safety of Medicines, which will last for three months.
Aristolochia is a herb used in Chinese medicine to treat fluid retention and rheumatic symptoms. But it has been a prescription-only medicine since 1997 because research has found that the herb can be toxic and cause kidney damage.
It can be easily confused with two other harmless Chinese herbs, Stephania and Clematis, used to treat similar problems. In 1993, 70 people in Belgium suffered from kidney failure after taking a slimming preparation in which Aristolochia had been used instead of Stephania. Both have the Chinese name Fangji.
The two UK cases of kidney failure happened after people took medicines with the herbal ingredient Mu Tong, the name used to describe at least four different plants including Clematis and Aristolochia. In both cases, the toxic herb was mistakenly used instead of the harmless plants. The Chinese herbal medicine industry is worth an estimated pounds 54m in this country, and is often used by people who want to seek less conventional medical relief for their skin or asthma problems.
Organisations representing Chinese medicine suppliers have voluntarily suspended use of Mu Tong and Fangji in a bid to ensure there is no confusion. "I have sent out a note to all our members informing them that Aristolochia is now banned," said Dr Lee Lin, president of the Chinese Medical Practitioners Association.
"I fully support any move towards regulation as long it does not add another layer of bureaucracy and helps to educate and inform the public about the benefits of Chinese medicine. Chinese medicine is safe but people should ensure they go to a registered practitioner." The ban came into effect yesterday and will last three months while the MCA consults the industry.
Officials are also considering whether to impose a permanent ban on the herbs which can be confused with Aristolochia. Herbal medicines are not subject to the same controls as licensed medicines and there have long been fears over their safety. Homeopathic medicines derived from Aristolochia are not covered by the ban because experts consider them too dilute to carry any risk of toxicity.
Debbie Shaw, an expert on the side-effects of Chinese medicines, said that responsible practitioners had already stopped using Aristolochia. She said: "There is no need to panic. People with these preparations should stop using them, then take them back to their practitioner to make sure they do not contain Aristolochia."