Almost 70% of fertility clinics either have no access to donor sperm, or find it extremely difficult to obtain, a BBC survey has revealed.
Who was surveyed?
The BBC talked to 74 out of the UK's 85 fertility clinics. Fifty said they either had no sperm or insufficient supplies.
Many reported waiting times of at least six months for couples needing donor sperm, and some were having to turn patients away.
The poll found 75% of donors are in just six clinics.
There are just 169 donors registered in the UK, all but seven at English clinics.
Northern Ireland has no registered donors at all, while Scotland has just one and Wales has six.
Why are the rules governing sperm donation?
Last April, the government ended the anonymity for people donating sperm or eggs for use in fertility treatment.
It meant children conceived this way could now identify their genetic parents once they reached 18, meaning they had the same rights to know their biological parents as children who had been adopted.
Did the rules apply to all donors?
No. The law did not apply retrospectively, so people who had donated prior to April 2005 were not affected by the change.
Why is there a shortage of donated sperm?
There are conflicting views.
Dr Allan Pacey, of the British Fertility Society believes the number of men volunteering to donate started to decline prior to the law change due to the anxiety it would apply retrospectively.
But Olivia Montuschi, of the Donor Conception Network, said there had been a change in the type of men thought to be suitable to be donors.
And she added many clinics had been opposed to the ending of anonymity, and did not believe the government would actually make the change.
She suggests it was clinics who "panicked" donors by saying that the law mighty be retrospective, or that donor conceived people would make huge demands on them.
What does the government say?
The Department of Health said some clinics have managed to sign up new donors, and others should follow their example.