Unions have accused the HSE of re-writing the Haddington Road Agreement.
A memo from the head of HR, Barry O'Brien, has been sent to staff requesting that they work a 39-hour week and take a pay cut instead of a 37-hour week with a cut to salary.
It comes as the HSE scrambles to meet savings targets after their pay bill savings came in €40m below the €150m target for this year.
Industrial Relations Officer with the INMO, Phil Ni Sheaghdha, says her union will consult with the implementation body for the agreement next week.