Garda overtime in 2017 cost €132 million, about 50 per cent more than projected, the Comptroller and Auditor General (C&AG) has found.
About one fifth of the overall budget (21 per cent) was spent on fighting organised crime.
The garda pay deal, which came into effect at the beginning of the year, is also estimated to have led to overtime costs of €28.3 million.
Commenting on the bill, the Department of Justice said since 2016 the response to gangland and serious organised crime has led to the need for more overtime.
"An Garda Síochána have made important progress in tackling the insidious threat of gangland and other serious organised crime," it said in the report, adding that gardaí had intervened in 50 incidents in which someone's life was in danger.
Overtime expenditure, it said, “is largely demand driven and can be difficult to predict with absolute accuracy”.
The C&AG accounting officer further noted the most effective response to organised crime was operational activity which includes surveillance.
“[THIS] would have the capacity to lead to particular suspects being apprehended at a time and location, which would render it highly probable that a conviction for attempted murder and associated crime could be achieved,” the report said.
“It is assessed that such investment leads to considerable savings in the longer term, arising from avoiding the significant expense of a murder investigation.”
However, despite this, the report found that management practices to control the overtime budget last year were “ineffective”.
The €132 million bill accounted for 12 per cent of overall spending on pay and compared to €38 million in 2014. Expenditure has exceeded estimate provisions for the last five years.
As early as February 2017, the Garda Commissioner and senior management were informed that the overtime spend in January alone had shown signs of being over budget.
However, the report stated that “any corrective actions taken to limit overtime costs were unsuccessful and the full year’s estimate provision for overtime of €88.5 million was exhausted by August 2017.”
“In the period to the end of the year overtime continued to be approved and paid without any curtailment.”
By October, the Department of Justice was resigned to a “significant overrun” in spending.
It was also concerned there was no indication of any governance measurement that would prevent a repeat of the situation in 2018.
Last year, there were 13,551 garda members and 2,192 civilian employees, as well as reservists and students. Overtime is paid at 1.5 times basic rates, and double on weekends.
There has been an increase of about 12 per cent in the number of officers receiving overtime between 2014 and 2017. The total number of overtime hours increased by 219 per cent in the same time while the average number of paid overtime hours increased by 185 per cent per officer.
Most overtime (about 75 per cent) is deemed “regular” - including court attendance, prisoner escorts, events and traffic plans.
In other countries, overtime accounts for just 4 to 5 per cent of policing expenditure compared to 12 per cent here.
A pilot programme is underway in the Dublin Metropolitan Region Eastern Division to improve roster and duty management with the aim of reducing overtime and this will later be rolled out elsewhere.
This September, a comprehensive review of overtime commenced and is due to conclude by the end of the month.