A sperm donor has fathered at least 150 children, it has emerged.

His extraordinary record was discovered after a mother who had a baby using a donation from the unidentified man mapped out his “family”.

Cynthia Daily raised the alarm after tracking the number of children by her donor following the birth of her son seven years ago.

The 48-year-old, from Washington, discovered that it was the largest “family” on the US Donor Sibling Registry, a website where parents are encouraged to report a donor child’s birth.

The case raises concerns about the spread of genetic diseases and fears that the offspring could inadvertently commit incest.

Sperm banks have also been accused of profiteering from high quality sperm by offering it out to dozens of would-be mothers.

Britain’s Human Fertilisation Embryology Authority has a legal limit of ten families per donor and there are similar measures in other European countries.

In the US, however, there is no such limit.

Wendy Kramer, founder of the Donor Sibling Registry, said: “The industry will tell you that the sperm goes all over the world so there is no chance of people meeting up - with the possible risk of incest - but we see people bump into each other randomly time and time again.

“This donor who has fathered 150 children is the largest we are aware of but in time he will have more children. It will just keep on growing.” - Daily