The Irish Haemophilia Society has claimed that over 200 of its members are being denied access to new high-tech drugs approved for use by the Health Service Executive to treat Hepatitis C.
It said the drugs offer a high rate of cure from the life-threatening virus, but are not being issued in seven designated hospital pharmacies due to a manpower problem.
IHS Chief Executive Brian O'Mahony said the drugs can offer a chance to cure the progress of liver disease, cirrhosis or premature death.
He described the delays as "reprehensible and indefensible".
The IHS said its members want the drugs to be dispensed with immediate effect.
The HSE has rejected the claims that patients with haemophilia are being denied access to the new drugs.
It said the medicines were approved and made available last year, and patients are being treated in the seven centres.
The HSE also said a small number of additional resources are required to accelerate the delivery of the service.
The funding for the drugs and the additional resources are provided for in the HSE Service Plan for 2013.
Around 245 people with haemophilia were infected with the Hepatitis C virus from the 1970s to the early 1990s due to contaminated blood-clotting products.
So far, 35 have died from the virus.
The two drugs involved were licenced in Ireland a year ago and approved for use by health authorities through specialised units. The treatment usually lasts a year.
The drugs target a particular genotype of the virus, which around 1,000 people in Ireland have.
The hospitals involved are the Mater, Beaumont, St James's and St Vincent's in Dublin; Cork University Hospital, Galway University Hospital and St Luke's Hospital, Kilkenny.