Researchers warn: Britain is suffering a shortage of sperm donors because they no longer have the right to remain anonymous.
Fertility experts are pushing for a recruitment drive among older men because of the lack of good quality sperm available.
More donors are needed but the change in the law in April is putting people off applying, the researchers say.
Children conceived from donated sperm or eggs since the change in the law will have the right to know the identity of the donor when they reach 18.
More than 1,000 applicants to the Newcastle Fertility Centre in the decade up to 2003 were questioned for the research published in the journal Human Reproduction.
It showed that the number of applicants in 1994 was 175 - but this figure dwindled to just 25 in 2003.
The sharpest fall came after 2000, when the anonymity issue was being debated in public, Sky News reports.
Dr Jane Stewart, of Newcastle University, said: "With the change in anonymity rules coming we saw a sharp fall in numbers and a change in the profile of applicants, perhaps reflecting the attitudes of different groups to anonymity."