The Prison Officers' Association (POA) has rejected by an overwhelming majority a deal aimed at reducing the annual overtime bill.
A proposal by the Irish Prison Service was rejected by 2,914 members of the POA with only 28 voting in favour of the scheme.
The offer was an annual payment of up to €10,300 to prison officers if they agreed to work 360 hours of overtime per annum. Under the deal this sum was fixed and would be paid even in the event that less than this number of hours was worked.
This proposal was the cornerstone of a plan by the Minister for Justice, Mr McDowell, to cut the annual overtime bill in the State's prisons, which will reach €64 million this year.
Prison officers are seeking €10,800, in exchange for annualised hours and for a pension contribution to be paid on the majority of that sum.