Sales of ‘secret’ paternity tests are surging, according to suppliers of DIY home kits.

The DNA tests, which can be carried out with simple cheek swabs, are leading to growing numbers of men discovering they are not the biological father of children they had been led to believe were theirs.

AlphaBiolabs, the leading British home test supplier, says up to 30,000 paternity tests are being performed in this country every year – and that the figures are rising by ten per cent per year.

‘Of these, around 20 per cent of men will learn they are not the father of the child they are testing,’ says the company’s director, David Thomas. He added that in some regions the figure is higher, including the North East, where it is 30 per cent.

Around 20 per cent of men will learn they are not the father of the child they are testing

The explosion in demand for the tests has been fuelled by the ease with which definitive DNA paternity results can now be obtained. For about £99, testing kits which promise 100 per cent accurate next-day results can be bought online.

Instead of requiring the physical presence at a clinic of both parties being tested, they involve only swabs taken from the inside cheeks of father and child, which are then packaged up and posted to the company.

As long as the man is named on the child’s birth certificate, or has parental responsibility, no permission is required from either the mother or child, meaning the tests can be carried out in total secrecy.

Some websites suggest DNA can be taken from children while they are asleep, to avoid awkward questions, particularly if the children are older.

In some US states, concern over this has led to a recent ban on DIY home DNA testing, with all tests now having to be ordered by a doctor or court official and conducted under their supervision. In Britain, there is no such legislation currently being considered.

Experts warn that the shock of learning a child is not biologically theirs can lead to severe emotional distress for some men, for which they may not be prepared.

Last week, The Mail on Sunday revealed the case of Moneysupermarket.com co-founder Richard Mason, who discovered the three sons he had raised as his own with his ex-wife Kate were not biologically his.

Richard Mason (left) with partner Emma (right) has revealed he discovered the three sons he had raised for more than 20 years were not his when doctors told him he had been infertile since birth

Mr Mason’s devastating realisation was the result of his being diagnosed with cystic fibrosis, which led doctors to inform him he had been infertile since birth.

After the diagnosis, he confronted his ex-wife and uncovered the truth that his sons had been conceived by another man with whom she had conducted a four-year affair.

The rising numbers of men turning to paternity testing suggests there are many who feel they may have been duped by women.

Mr Thomas said: ‘Sometimes men will be delighted to learn they aren’t the father – usually when a woman with whom they have been having a casual relationship tells him he has fathered a baby and he can prove otherwise. In other cases it’s the mother who’s ordered the test to “shut the father up”.’