Cash-strapped Stormont departments are spending almost £30,000 a day on overtime, the Belfast Telegraph can reveal.
Civil servants worked an astonishing 709,636 extra hours during the last 12 months, running up a bill in excess of £10m.
The biggest spender was the Department of Agriculture, which shelled out almost £2.7m in overtime payments to its staff.
Two other departments - Regional Development and Social Development - also had bills in excess of £2m.
The revelation has prompted calls for an urgent review of overtime spending.
Details of departmental expenditure were released to this newspaper following a series of Freedom of Information requests.
The total outlay on overtime during 2010/11 amounted to £10,663,738, excluding the newly-formed Department of Justice, whose figures are not yet available.
Although overall expenditure has fallen compared to the previous year's total, three departments saw their overtime spending increase in this period. These were Culture, Arts and Leisure; Employment and Learning, and also Finance.
SDLP Assembly member Patsy McGlone said there was an increased responsibility on departments to justify expenditure.
"Every department has to have a serious look at how much it is spending on overtime given the current financial constraints," he said.
"I understand there will be occasions like last winter's frost and water crisis when overtime cannot be avoided, but that has to be balanced against excessive overtime in other departments.
"I sincerely hope that departments will take a look at these figures and place a very close watch on what overtime is required to ensure there is no overspending."
Emma Boon, campaign director at the TaxPayers' Alliance, which monitors spending by public bodies, said urgent action was needed to reduce the expenditure.
"It's unbelievable that so much is being spent on overtime by departments," she said.
"These figures will anger many private sector workers who don't get paid when they put in extra hours, it's just part of the job to them."
According to the figures, staff at the Department of Agriculture had the highest overtime bill - £2,696,146 for 183,676 hours' extra work. This was closely followed by the Department for Regional Development, which ran up 166,772 hours costing £2,559,966.
In a statement, the former department said: "DARD's overtime costs arise from our operational needs in meeting legislative requirements and providing a service to the rural community and the wider public.
"The department provides much out-of-hours service, for example, 24-hour meat inspection cover, animal disease testing, flood prevention and alleviation work, responsibilities for student welfare for under-18 year-old residential students at CAFRE and for the delivery of training courses and workshops to farmers in the evenings when farmers are available to attend. These are activities which by their nature cannot be carried out during normal working hours."
Six-figure overtime bills were also accrued by the Department of Social Development (170,233 hours costing £2,357,520) and the Department of Finance and Personnel (74,963 hours costing £1,277,229). Both DSD and DRD have slashed their overtime expenditure since last year.
According to figures for the 2009/10 financial year, DSD spent £5.2m while DRD's outlay topped £3.5m.
The Civil Service has a lengthy policy on the allocation of overtime. Hours worked at management's request in excess of conditioned hours are regarded as overtime. Staff asked to work overtime on days Monday to Saturday are allocated a rate of time and a half plus a Saturday premium. For those who work Sundays, there is double time plus a Sunday duty premium. Senior staff are given time off in lieu for the overtime incurred.