The Government's genetics watchdog will today warn of a rise in private firms cashing in on the public interest in DNA profiling and dieting.

At a conference in Edinburgh, Sir John Sulston, one of Britain's most eminent scientists and a leading member of the Human Genetics Commission (HGC), will call for new regulations to tackle the growing industry of companies offering over-the-counter DNA testing.

Sir John, who won the Nobel Prize for Physiology in 2002, fears a growth in companies charging between £300 and £900 to advise people on what they should eat and what supplements they should buy on the basis of their genetic make-up.

He believes the practice is dangerously misleading and a "waste of money" because the science is not yet sufficiently advanced.

Nutrigenetics, also known as nutrigenomics, is the practice of matching different genetic make-ups with tailored diet and supplement plans.

There are a number of companies in the US and UK offering packages which claim to help people lose weight, increase life expectancy, avoid disease and "look better".

Most request a sample of DNA, such as cells from a mouth swab, to be sent through the post. Customers are then sent or handed their results with guidance on what diseases they are most at risk of, how best to change their lifestyle and what supplements or diet plans to follow.

Sir John, who was a leading member of the UK's race to map the genome in 2000, believes the growing trend for private companies offering "nutrigenetics" could add to the growing burden on the NHS if people are given inappropriate or worrying advice.

"It is a growing concern that people are selling DNA tests which purport to tell you what sort of diet you should eat and how that links into the dietary supplements they are selling," he said.

"This is simply misleading because the genetic comprehension of lots of these bodily functions is marginal.

"There are 20,000 genes in the human body and there are a lot of common variants.

"The variants themselves are relatively well known so we can say this particular variant will mean you are slightly more susceptible to high cholesterol."

Sir John continued: "The trouble is that we find the influence of any one particular gene so small that most people would be just as well off by improving their lifestyle in general rather than taking a drug to deal with it.

"In most cases it is just a waste of money but there is also a danger of people getting poor advice if the test indicates there is something seriously wrong.

"On the NHS people get counselling if they are told they have a variant which predisposes them to a particular disease. The problem is also in the interpretation of deciding from the test what is important and what is not."

He added: "At the moment there are no statutory limitations. We need to ensure that testing is available on the NHS for important conditions and that for those who choose to get the tests done, that they are aware of the situation. We need to tighten this up and set up rules.

"Done properly, there are tests critical in determining which people are much more susceptible to getting certain types of cancer.

"It is very distressing to find out this kind of information over the counter that is why it is vital the NHS is financed in this area."

The two-day conference of the commission, the UK body which advises both Westminster and Holyrood on developments in human genetics, will consider a range of ethical and social issues involved in developments in DNA.

The HGC, which is chaired by Baroness Helena Kennedy, was in the news last month in the row about allowing the development of hybrid embryos composed of human and animal materials. The commission opposed a proposed ban by the Government.

Nutigenetic testing has already proven controversial in the UK market. In 2002 the Body Shop took a genetic test product off their shelves after warnings from the UK lobbying watchdog GeneWatch UK.

The genetic tests, carried out by the company Sciona, offered a personal eating plan for the consumer. GeneWatch UK said the tests were unregulated and misleading and should not be conducted by "vested interests".

It said: "Promotion of widespread genetic testing by vested interests distorts the health research agenda, diverts resources from more valuable approaches and risks a loss of public trust in medical research."

Amid growing concerns about the lack of research on the effectiveness of nutrigenetic diets, the Wellcome Trust has provided funding for a two-year research project at Exeter University.

The Genetic Health clinic in London's Harley Street offers this DNA testing service for £265. Their test kits claim to optimise diet and regulate body mass index, slow down the aging process, balance out hormonal disturbances and regulate brain chemicals.

Nobel Prize winner

Sir John Sulston's honours and accolades create a particularly impressive curriculum vitae. Now, 65, he won the Nobel Prize in Physiology or Medicine in 2002 for his work mapping the cell structure and genetics of the nematode worm, caenorhabditis elegans.

In 1992, Sulston was appointed the first director of the Wellcome Trust Sanger Institute in Cambridgeshire which made the UK's contribution to the international Human Genome Project.

Following publication of the first draft sequence of the human genome in 2000 he was listed among the UK's 100 most powerful people by a national newspaper.

Sir John received his knighthood for services to genome research in the 2001 New Year's Honours. He stepped down as director in September 2000 but continues to work on C. elegans at the Wellcome Trust Sanger Institute.

Sir John is the co-author of The Common Thread: A Story of Science, Politics, Ethics and the Human Genome.