The Department of Health says health boards must ensure that public hospitals use a maximum of 20% of their capacity for private patients.
It was responding to figures which show that many hospitals are giving more public beds to private patients than they are allowed under current agreements.
New figures obtained by the Labour Party show that two thirds of publicly-funded hospitals are over the bed quota.
The Opposition says it means public hospital patients are being forced to wait longer for treatment.
However, consultants say the issue is one of capacity in the system.
The 2002 figures show that the total number of private patients as a percentage of all hospital patients, was 25%.
St John's Hospital in Limerick had the highest percentage of private patients at 57%, while more than 40% of the patients in six other hospitals were in private care.
