A new policy stopping people who lived in the UK for five or more years from donating blood in Ireland comes into effect today.
The Blood Transfusion Service introduced the move in an effort to minimise any possible risk of transmitting variant CJD through blood banks.
The policy applies to anyone who lived in England between 1980 and 1996.
The BTS said it expects to lose around 20,000 donors each year as a result.