Edzard Ernst, a professor of complementary medicine, also described the logic behind homeopathy as bizarre and accused homeopaths of lying to their patients.
The NHS spends around £4million a year on homeopathy, despite calls from the British Medical Association for the funding to end.
The discipline – which has won the backing of Prince Charles – claims to prevent and treat diseases by using dilute forms of materials that in higher concentrations could produce the symptoms of the condition.
Homeopaths also believe that the greater the dilution of the medicine, the more potent the potion, and so ingredients are mixed in tiny amounts with water or alcohol.
A typical remedy could have one part of an ingredient to one trillion, trillion parts of water. Although scientists argue the potions are so dilute they are unlikely to contain any of the original substance, homeopaths claim the water retains a ‘memory' of the active ingredient, which it passes to the body to help fight the illness.
But Professor Ernst said that even if an ultra-dilute homeopathic solution was somehow different from pure.
Writing in the Society of Biology's magazine, The Biologist, he said: ‘How would this difference explain positive health benefits? The water in my kitchen sink also differs from pure water after the washing up but this does not mean it is good for my health.'
Professor Ernst, a former homeopath who now researches complementary medicine at Exeter University, said the treatments could be dangerous if people chose them over conventional medicines with proven benefits.
He accused homeopaths who cite studies showing the treatments work of ‘cherry-picking' results.
However, the professor saved his most scathing criticism for the Government. He said if a homeopath doesn't tell a patient that the treatment is worthless, he is not telling the truth. Modern medical ethics state that patients must be fully informed and telling lies to patients is not acceptable.
‘It follows that the Government's decision to continue offering homeopathy on the NHS is not ethical.'
The Commons science and technology committee recently criticised state funding of the treatments, saying it conferred scientific legitimacy.
Dr Mark Downs, chief executive of the Society of Biology, said: ‘The UK spends literally billions of pounds every year ensuring that the new and existing conventional medicines we take are effective, safe and fit for purpose.
‘It makes no sense to allow other treatments through public expenditure to be made available without application of the same standards.'
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