Bourn Hall, which has clinics in Cambridge, Colchester and Norwich, had previously offered free IVF treatment to the partners of men who shared their sperm, but they found that they did not have enough donors with high-quality sperm.
After conducting a survey into men's attitudes towards donating sperm, they found that the biggest motivation was knowing that they could help someone who was having difficulty conceiving.
Dr Mike Macnamee, Chief Executive of Bourn Hall, said: 'We were the first clinic to introduce sperm freezing and we have our own sperm bank, but demand is rising and there is a national shortage. When a couple comes to the clinic for treatment and testing reveals that a man has "super sperm" then we offer them free IVF treatment in return for sperm donation.
'The recent study has indicated that altruism is a powerful motivator, so we have decided to extend this offer to allow donors not requiring help themselves to nominate someone they know for free IVF treatment.'
Donors must be aged 18–40 and be in good health. If accepted, they can choose to nominate a friend or family member to receive one free cycle of IVF. Alternatively, they would be offered up to £35 per sample - a compensation level set by the Human Fertilisation and Embryology Authority in 2011.
Dr Macnamee stresses that potential donors are screened to make sure they aren't being pressurised into donating. Donors also receive counselling to ensure that they understand the implications of their choice. All donors are anonymous until any children conceived using their sperm turn 18, at which point they can choose to receive identifying information about the donor.
Jackie Stewart, an independent fertility counsellor who supports Bourn Hall patients, said: 'The majority of men have not even considered donating sperm and may think they are too old. However, many would try and help if someone they knew was struggling to conceive.
'With this knowledge, it is good to talk about your situation with close friends and family and also to explain how much a baby would mean to you. There may be someone in your wider circle of friends and family that is in a position to offer help and would find it rewarding to do so.'