Soaring sales of 'dangerous' do-it-yourself DNA test kits: Number of websites selling products doubles in two years

38 British websites now offer home testing kits - which can cost up to £300

Paternity and genetic ancestry tests are the most popular

Tests which claim to reveal vulnerability to diseases are also up

Sales of DNA tests for everything from the risk of developing life-threatening diseases to catching out cheating partners are booming.

The number of British websites offering home testing kits and services has doubled to 38 in just two years, research has revealed, with companies charging fees of up to £300.

DIY paternity and genetic ancestry tests are the biggest sellers, however sales of tests claiming to reveal a predisposition to certain diseases are up 14 per cent a year.

DIY: Paternity kits such as this one, being bought from a U.S. clinic, are among the most popular products

The revelation by Angelina Jolie that she had a double mastectomy because she had a greater genetic risk of developing breast cancer triggered a spike in tests.

Genetic tests also now exist for a host of serious inherited illnesses, such as Huntington’s disease or Parkinsons.

However, the advances open up potentially devastating consequences for people who get bad news about their risk of developing a fatal illness.

Taking out life insurance to provide for loved ones or getting approval for a mortgage could become impossible if consumers are required to divulge information on application forms.

Interest in ancestry testing has been sparked by endorsement from celebrities who claim it has allowed them to trace back their origins through the generations.

For example, the actor Tom Conti spoke of his shock – and pleasure – on discovering, via DNA tests, that he is related to Napoleon.

Comedian Eddie Izzard, meanwhile, made a TV programme about how he traced his family tree back 10,000 generations, with the help of DNA analysis.

Sales spike: Angelina Jolie's revelation that she chose to have a double mastectomy because she had a genetic risk of breast cancer increased interest in testing kits

However, scientists have raised serious questions about the accuracy and value of such testing.

DNA testing also has a more sordid side as seen on controversial TV programmes like ITV’s controversial Jeremy Kyle show, which uses DNA paternity tests as the main tool to settle family disputes.

Some firms also allow customers who are suspicious of husbands or wives to send off underwear to discover whether other human DNA is present and if so, the number and gender of people found.

There are also serious questions about the accuracy of DNA tests to establish a disease risk, which could mean consumers are being seriously misled about their health.

The commercial potential of DNA testing has been identified by Anne Wojcicki, the wife of Google entrepreneur Sergey Brin. She is co-founder of a company called 23andMe , which is selling services and kits via mail order around the world, including the UK.

A new British website – Dnatestingchoice.com – claims to offer a Trip Advisor style review system for DNA tests and websites selling them.

It is the brainchild of biology scholar and online marketing expert, Craig Macpherson, who highlighted the fact that the Government supports the idea of creating an anonymised DNA genetic database of the nation to understand what the NHS should be spending its money on.

Mr Macpherson said: ‘Our DNA is a map of our family history and in particular a key to understanding our risk of predisposition to certain diseases.

‘I share the Health Secretary Jeremy Hunt’s view that Britain should become the first country in the world to routinely sequence people’s genomes to help the NHS plan for our futures.

‘This information is invaluable for helpings a new industry of genetic counsellors, which I believe is required, to recommend lifestyle changes and treatments to enable patients to stay healthy for longer.’

He added: ‘The internet is full of companies selling over 900 different tests with no standard pricing structure. We aim to show people what is available and what are the best buy, allowing consumers to share their experiences and make informed choices after reading public and expert reviews alongside the very latest information on genetics.’

He said the most unusual genetic tests currently being offered include one that claims to find an ideal partner based on DNA characteristics. Testing of pets, to establish the breed mix, are also being offered.

Many scientists are sceptical about the value of DIY home DNA testing, suggesting it could cause real harm.

Dr Helen Wallace, of GeneWatch UK, said: ‘There are major concerns about the private genetic testing market.

‘It is unregulated, much of the information people get is misleading or unreliable and genetic tests are a poor predictor of the big killer diseases.

‘And there is also the danger of people receiving scary surprises without the presence of a doctor for which they are not prepared.’

The organisation Sense About Science has published a leaflet highlighting the pitfalls of using ancestry tests.

Steve Jones, emeritus professor of genetics at University College London, said: ‘In a long trudge through history, two parents, four grandparents and so on, very soon everyone runs out of ancestors and has to share them.

‘As a result, almost every Briton is a descendent of Viking hordes, Roman legions, African migrants, Indian Brahmins, or anyone else they fancy.’

Mark Thomas, professor of evolutionary genetics at UCL, said: ‘Ancestry is complicated and very messy. Genetics is even messier. The idea that we can read our ancestry directly from our genes is absurd.