Some local authority workers in 11 county councils will have to work longer hours from next March according to a new Labour Relations Court recommendation.
Local government managers had sought to standardise the working week for local authority administrative employees at 35 hours. Outdoor staff already work a 39-hour week.
However, unions had argued that increasing working hours would constitute a reduction in a pay rates and was precluded under the Croke Park Agreement.
The recommendation reveals that while 18 of the country's 34 local authorities already have a 35-hour working week, 16 work less than that, including the country's biggest local authority Dublin City Council.
The shortest working week is in Galway county at 32 hours 55 minutes.
Four councils - Clare, Galway City, Limerick County, and Meath - have a working week of 33 hours.
In Dún Laoghaire-Rathdown, Fingal and South Dublin County Council, the working week is 33 hours and 15 minutes.
Local authority employees in Cavan, Dublin City Council and Waterford City work 33 hours 45 minutes a week.
Limerick City Council staff work for 34 hours ten minutes a week.
In Leitrim, Longford, Roscommon and Westmeath, the working week is 34 hours 45 minutes.
It has recommended that the 18 local authorities that currently have a 35-hour working week will retain it.
Those who currently work between 34 and 35 hours will retain their existing arrangements.
All those who currently work below 34 hours will see their working hours increased to 34, with part-time staff seeing a pro-rata increase.
All new recruits or promoted staff will work a standard 35-hour week.
The new arrangements will be implemented on 1 March 2013.
The Labour Court said the recommendation was on an interim basis pending the emergence of public service wide proposals on the establishment of a standard working week.
Sources at the Department of Public Expenditure and Reform welcomed the ruling, but said it was essential that local authority management used the extra hours effectively to improve service delivery to the public.