Almost 70% of fertility clinics either have no access to donor sperm, or find it extremely difficult to obtain, a BBC survey has revealed.
Mark Jackson has no doubts about donating
Mark Jackson, 38, from Doncaster, became a sperm donor last year after reading the BBC News website.
"I was reading about tsunami in January last year and saw that the site was also running a story about lifting the anonymity of gamete donors which had a link to a website.
"I got some information and phoned clinics in Leeds and Sheffield, but they said they weren't recruiting".
Mark was eventually accepted as a donor at St Mary's Hospital in Manchester.
He doesn't have children, but says he is not worried about children "turning up on his doorstep" in 18 years time.
"I'm not worried about it whatsoever. To be quite honest I think, if they do, it'll probably just be out of curiosity rather than anything else."
He thinks donating was a worthwhile thing to do.
"I spoke at a conference, and ladies came up to me afterwards and showed me photos of their children who were fathered with donor sperm.
"It makes you feel really good."