Fertility clinics are facing a "national crisis" because of a shortage of sperm donors, say experts.
The UK is suffering from a shortage of sperm donors
Infertility Network UK said a change in the law, which abolished anonymity for donors, has stopped men volunteering.
But other campaigners said a lack of awareness of the need for sperm donors was the reason for the fall in numbers, not the law change.
The number of sperm donors has been steadily declining over the past number of years, HFEA figures show.
In 2000, 325 sperm donors were newly registered with the HFEA but in the first six months of 2005, only 99 men were registered.
Around 500 sperm donors and 1,500 egg donors are needed each year.
Since the 1st April 2005, people donating sperm and eggs have not had the right to remain anonymous.
But the HFEA said there had been no sudden drop in donors coming forward after the law came in.
Clare Brown, chief executive of Infertility Network UK said there were "enormous barriers" to recruiting sperm donors and fertility clinics had infertile couples on their waiting lists who they couldn't treat.
"The clinics are struggling and that's putting it mildly. It's difficult to say 100% that the removal of anonymity is or isn't the reason but this is what everybody was concerned would happen.
"It started to decrease even while the law was under discussion."
She said Infertility Network UK, the Department of Health and the National Gamete Donation Trust all had to work together to develop a national campaign.
"Unless we do something about it, things will get worse. Men are obviously not donating anymore and we need to raise awareness."
Dr Allan Pacey, Senior Lecturer in Andrology at the University of Sheffield and Secretary of the British Fertility Society said there were only around 20 clinics who were still recruiting sperm donors.
"It is true that the number of men enquiring to be sperm donors begin dropping in the years leading up to April 2006, but we believe that this was almost certainly due to the anxiety about whether or not the change in law would be retrospective or prospective, which at that time was unknown.
"Sadly, the government took a long time to make that decision and as a consequence many centres had to close down their sperm donor recruitment operations because too few men were coming forward to keep it economically viable.
"Today, many NHS clinics are finding it hard to re-start donor recruitment because there are now not enough resources available to do so."
But Laura Witjens, chair of the National Gamete Donation Trust said that although there was a lack of sperm donors in the UK it was not because men could no longer remain anonymous.
"One of the main issues is there is a general lack of awareness about the need for sperm donation.
"Also the clinics in the UK are no longer recruiting - a lot of sperm banks have closed their doors.
"We need a big recruitment campaign but also clinics need to be area of how to recruit properly," she said.