The Association of Garda Sergeants and Inspectors has said its members want to examine how any cuts to discretionary and administrative overtime will impact core policing services.
The Garda Commissioner said the force will significantly exceed the budget for this year and this is not a sustainable position.
Commissioner Drew Harris said overtime will still be available for specific policing security operations, but only with approval.
John Jacob, General Secretary of the AGSI, said: "I think we need to examine it closely, we haven't had a chance as an association to examine what the commissioner has issued.
"We have to be sure that the cut in overtime does not impact on the delivery of core policing services which do not require overtime."
Garda chief sparks alarm after ‘bringing hatchet down’ on overtime
Directives are being issued to divisions nationwide and specialist units as part of a plan by Garda Commissioner Drew Harris to cut the overtime bill by 30%.
Senior sources said the commissioner has “brought the hatchet down on overtime” after Garda HQ figures showed the overtime bill was €15.5m in the red by July and would hit €30m by the end of the year.
The day after taking office, Mr Harris said he was looking at bringing the overspend “back in line”.
Directives have been issued in the Dublin region, the eastern region, and by Special Crime Operations, which covers six national bureaus. Similar directives are expected in remaining regions in the coming days.
The Garda Representative Association called it an “extraordinary development”, saying it would impact on all gardaí doing their job, in particular, those investigating crime gangs.
A number of sources said the overtime ban would impact specialist high-profile operations, including Thor (burglary gangs) and Hybrid (Kinahan-Hutch feud).
Garda HQ said this will not be the case, while assistant commissioner for Dublin Pat Leahy said “clarity has been sought” regarding operations such as Hybrid and Thor and public-order weekend patrols.
In his directive, Mr Leahy said: “With immediate effect, all discretionary expenditure is hereby cancelled.”
One source said Armed Support Unit patrols in Dublin have dropped from seven last year to five in January to three now.
A directive issued in the eastern region said: “In an effort to bring the national Garda overtime budget in line by the end of the year the national budget allocation shall be corrected by 30%.”
A directive issued by the assistant commissioner for Special Crime Operations to serious crime units said: “With immediate effect all discretionary expenditure across all subheads is hereby cancelled.”
Overtime is to be sanctioned only for non-discretionary duties, such as courts and examination of scenes of crime.
Mr Harris said the organisation “must work within the annual budget”.
He said: “This has been stressed continually to Garda managers throughout 2018. Regrettably, An Garda Síochána will significantly exceed the budget this year. This is not a sustainable position. To minimise the impact on policing and security activity, while reducing the excess spend before the end of the year, I have cut discretionary overtime and administrative overtime.
"Overtime will still be available for specific policing/security operations, but only with approval.”