New figures published by An Garda Síochána shows spending on overtime has increased by 58% over the corresponding period last year to €60.6m.
It means each garda, on average, earned about €4,555 in overtime in the first six months of the year.
Some gardaí would have earned considerably higher amounts as overtime is restricted to members at garda, sergeant and inspector rank.
Expenditure on overtime has more than doubled in nine divisions, including the three Garda divisions in Cork.
In Cork City, overtime cost four times as much in the first half of 2017 as over the same timeframe last year.
The overtime bill for gardaí in Cork City was over €1.8m this year compared to around €456,000 for the corresponding period in 2016.
Large increases in overtime have also been recorded among gardaí in Donegal, Galway, Kerry and Sligo/Leitrim.
The latest increases are becoming a concern as expenditure on overtime had already been growing rapidly in the last few years and had more than doubled in the past five years.
It went from €41.6m in 2012 to €90m in 2016, including a 61% rise last year with gardaí earning an average of almost €7,000 each for working additional hours.
The latest rise comes at a time when it was expected the requirement for gardaí to work overtime would be falling because of a large intake of new recruits and the increasing civilianisation of the force.
At a meeting of the Policing Authority in Dublin last week, Acting Garda Commissioner Dónall Ó Cualáin conceded the force had already overspent its overtime budget by 53% so far in 2017.
He attributed the soaring costs to the effect of a recent pay agreement reached with Garda representative bodies to prevent them from taking industrial action.
The new pay deal includes extra money for periods of time before gardaí begin their work shifts.
The payments are for a 15-minute period that gardaí spend “on parade”, which is a largely historical practice of preparing for a new shift.
Mr Ó Cualáin admitted the extra payment had “taken a big chunk” out of discretionary expenditure available to Garda management.
“We are very anxious to ensure that, in as much as we can, we can work and do our operations out of given resources and ensuring we use our rostering arrangements to get our best bang for our buck in that regard,” he said.
The force’s top civilian official, chief administrative officer Joseph Nugent, said gardaí were continuing discussions with the Department of Justice about the issue. However, he pointed out overtime was necessary to deal with organised crime and preventing deaths.
The overtime bill for civilian staff in An Garda Síochána has also risen sharply in the first half of 2017 — up 63% to almost €661,000.
The current Garda strength is 13,300 combined with 2,044 civilian staff.
In its 2017 spending review, the Department of Public Expenditure and Reform said the Garda overtime bill should be slashed to bring it to “sustainable levels”.
Overtime costs account for 9.3% of the Garda payroll budget but officials believe it should be brought down to 4%-5% in line with the international norms for police forces.
“There is a risk that the existing high levels of overtime will become embedded in the system,” they warned.
The basic overtime rate is €24.10 per hour for gardaí recruited before April 1995 and between €15.74 and €25.90 for newer recruits based on length of service.