The World Health Organization (WHO), UN Children's Fund (Unicef) and UNAIDS attacked Matthias Rath's advertisements as misleading and potentially dangerous.

The ads, along with flyers distributed by Rath and material posted on his website, claim that antiretroviral drugs damage all the cells in the body and that a combination of micronutrients can roll back HIV.

He claims that an "AIDS genocide" is unfolding thanks to what he describes as a cartel by the pharmaceutical industry.

"These advertisements, placed in the international press, are wrong and misleading," the joint statement by the UN agencies said. They added they were "extremely concerned" that they had been quoted out of context by Rath to bolster his claims.

"Misrepresentations of this sort are both dangerous and unhelpful," they said.

The statement went on to reiterate existing UN advice on nutrition for people living with HIV or AIDS.

Vitamins can't replace treatment

Published in 2003, these guidelines say a sound diet that provides all the essential vitamins and minerals is important for people with the AIDS virus, for it can help strengthen the immune system.

Vitamins and nutritional supplements alone cannot substitute for a balanced diet or replace treatment, the UN agencies said.

"In countries where it is widely available, antiretroviral therapy has turned AIDS from a 'death sentence' into a chronic but manageable disease," they said. "As with any other drugs, antiretroviral treatments do have side effects that have been documented in clinical trials."

The riposte was prompted by a series of ads placed last week by Rath in The New York Times and The International Herald Tribune, UNAIDS spokesman Dominique De Santis said.

The website says it is run by an organization called The Dr Rath Health Foundation, "a non-profit organization dedicated to the promotion of natural health through research and education worldwide."