Sperm from a donor who unknowingly carried a gene that raises the risk of cancer was used to conceive almost 200 children across Europe.

A major investigation revealed the sperm was not sold to UK clinics, but some families did use the sperm while having fertility treatment in Denmark.

Some children have already died and many more with the gene will go on to develop cancer in their lifetimes.

Denmark’s European Sperm Bank has admitted the sperm was used to make too many babies and sent their “deepest sympathy” to families affected. It is understood that the women have all been informed.

The investigation has been conducted by 14 public service broadcasters, including the BBC, as part of the European Broadcasting Union’s Investigative Journalism Network.

Children across Europe including the UK have been fathered by a sperm donor who carries a cancer-causing gene (stock image) (PA)

The BBC reported that the man was paid to donate sperm as a student and that his sperm was used for around 17 years.

Although he was healthy and passed all the screening checks he had changes in his DNA which meant the TP53 gene – which has the crucial role of preventing the body’s cells turning cancerous - was damaged.

The affected gene is not in every part of the donor’s body, but it is in 20 per cent of his sperm.

That means the children he has fathered will have the mutated gene throughout their body - a condition known as Li-Fraumeni syndrome.

People with this syndrome have up to 90 per cent increased risk of developing cancer before they turn 60.

This includes breast cancer; brain tumours; osteosarcoma; soft tissue sarcomas and childhood cancers.

Li-Fraumeni is a “rare syndrome”, according to an article from the National Institutes of Health in the US, adding that there are likely over 1,000 multi-generational families with the syndrome around the world.

Affected people have regular monitoring to look for tumours.

The European Sperm Bank said the mutation can not be detected in screening and said it "immediately blocked” the donor once the problem was discovered.

Doctors raised the alarm at the European Society of Human Genetics this year. They found 23 children with the variant out of 67 children known at the time. Ten had already been diagnosed with cancer.

The BBC reported at least 197 children are affected, but explained data has not been obtained from all countries so the figure may be higher.

The sperm was used by 67 fertility clinics in 14 countries.

In the UK, a donor’s sperm can only be used to create children in up to 10 families.

But in different countries, the limits are different.

The HFEA confirmed that the sperm was not distributed to licensed UK clinics.

Peter Thompson, Chief Executive of the HFEA, said:** **“We can confirm that the Danish Patient Safety Authority has informed us that a very small number of UK women have been treated in Danish Fertility clinics with this sperm donor.

“We understand that they have been told about the donor by the Danish clinic at which they were treated. As the UK regulator, we only collect or hold information about treatment which takes place in the UK. As the treatment took place at Danish clinics, further enquiries should be directed to the competent authority in Denmark.”