Garda Commissioner Drew Harris has said he has cut discretionary and administrative overtime because An Garda Síochána will significantly exceed its budget this year.
The overtime budget has been overspent by €20m so far this year and Commissioner Harris said this was not a sustainable position.
The decision will affect certain court proceedings and escorts, the examination of particular scenes of crime and deportation or transit orders.
However, the Commissioner has stressed that overtime would be available for specific policing and security operations.
The move has been strongly criticised by the Garda Representative Association (GRA), which has described the decision as "extraordinary".
An Garda Síochána has a €91m overtime budget, but by the end of the year its overspend could reach €30m.
Commissioner Harris said that the gardaí must work within its budget and he has therefore cut discretionary and administrative overtime.
Two senior officers have already issued directives to that effect.
The Assistant Commissioner in charge of Special Crime Operations, which tackles organised crime, has told gardaí no more discretionary overtime will be sanctioned, except in exceptional circumstances.
In a separate development, a second senior officer has also banned overtime for all administrative and Sunday work.
Gardaí there have also been told that no overtime is to be incurred for court escorts or for pro-active policing operations.
The GRA says the move will impact on the ability of frontline gardaí to investigate the activities of crime gangs, particularly in Dublin.
The association also says that overtime is essential for gardaí to provide an effective policing service and has called for the agreed overtime to be reinstated.
