Are you suffering from depression, substance abuse, obesity, stress, impotence, domestic problems or even a jinx? Then the good Sheikh can help you. He even solves marital problems, helps you with job interviews and, get this, is also in the business of dealing with anti–social behaviour. Pay after results, only one minute from Plaistow Station.

Sound fishy? How can you be so sceptical? Surely if he passes the watchful gaze of the advertising sales people at Independent News & Media, the billion–pound multinational corporation which publishes the Independent newspaper and London freesheets Midweek and Ms London, then this healing Sheikh must be kosher. After all, INM only have their readers' best interests at heart — after the bottom line of course. And the bottom line, it seems, depends on the Sheikh, assorted 'professors', West African marabouts and more healers and clairvoyants than you can throw a crystal ball at.

There is a disclaimer, of sorts, on the classifieds pages warning readers to use 'common sense' when parting with their money. This, presumably, absolves INM from all legal responsibility should the cures turn out to be bogus. Whether the same can be said for INM's ethical responsibility to their readers we'll never know: their classified ads manager wouldn't "entertain interviews about our policy for accepting advertising".

But why dwell? INM aren't the only publisher to turn a blind eye to where their advertising money comes from. The fact is that such mumbo–jumbo will appear as long as nobody kicks up a fuss, and even then there is a get–out clause for nonsense, as long as it bears the label 'spiritual'.

One giant poster that blights a busy market street in South London advertising Peniel Church Brentwood, an evangelical Christian congregation, screams 'Miracles, Healing, Faith' at passers–by. Readers might be forgiven for thinking that the poster claims the church will dispense miracles and healing in return for faith. Not so, says the Advertising Standards Authority, which "considered that the references to 'healing' and 'miracles' … referred to spiritual healing and miracles" (their emphasis). It stated further that "readers were unlikely to be misled by the advertisement". Luckily the poster has a telephone number, making it a simple matter to call Peniel Church for clarification. What exactly do they mean by 'healing'?

"We have seen people be healed of sicknesses and diseases," said the person on the other end.

"What, real illnesses?"

"Yes"

"So it's not just spiritual healing?"

"No"

The poster advertises healing, the church confirms they mean real healing, and yet the ASA does not feel compelled to step in because it regards anything to do with religion as 'spiritual' and therefore outside the mundane realm of consumer protection. In a sense, it's a bit of a put–down of these outfits if even the ASA, the friendly face of an industry devoted to creative interpretations of reality, considers them too far out to take seriously. But this doesn't help those who are conned into parting with their money or convictions in return for questionable 'help'. So what to do?

Allan Henness, a humanist from Glasgow, has made a number of complaints to the ASA about misleading adverts for traditional Chinese medicine and magnetic health products. Henness concentrates on unscientific claims that cannot be fobbed off as 'subjective statements'. "Most people's understanding of science is appalling. I'm an engineer so I have a science background. I'm not an expert but I can tell that a lot of these things are suspect."

What about free speech? "They are not free to mislead people and con them, especially if there is a financial advantage in there for the advertisers. And of course I am free to complain about them."

Another campaigner for scientific truth is Ben Goldacre, whose weekly 'Bad Science' column in the Guardian tears to shreds the pseudoscience on which many alternative health therapies and products are based. "The cultural orthodoxy has become that all nonsense invented by New Agers in California is automatically true until proven otherwise," he says. "I thought it was about time somebody did something about it. And to my delight I get about 50 to 100 emails every week; half of them are tips, a quarter of them are abuse and a quarter of them are fan mail from professors in molecular biology."

Goldacre says his main objection to alternative therapies is not that they are making money out of people with fairly minor physical ailments — "there's nothing wrong with the placebo effect", he says — but the intellectual dishonesty.

"All of this sort of stuff starts to undermine the public understanding of science and promotes the public misunderstanding of science and that's when it becomes offensive to me." A particular subject of his ire is TV and newspaper health pundit Gillian McKeith: "I find it bizarre that there is someone on national TV who says you should eat dark green leaves because they contain lots of chlorophyll and chlorophyll will really oxygenate your blood. I just find that amazing because it is so wrong. It's like saying Switzerland invaded Poland in 1939.

"It's just wrong to promote the public misunderstanding of science. How can we collectively make a decision about mass immunisation or genetically modified food if our national news media are actively promoting misunderstanding of science?"

Next time you see an ad that looks too good to be true, or read another crackpot remedy for irritable bowel syndrome, don't suffer in silence. Put pen to paper in defence of reason, and let us know how you get on: letters@newhumanist.org.uk