Over £40,000 a day is being spent on overtime at Stormont departments, it can be revealed.
Civil servants worked more than a million extra hours last year, running up a bill of nearly £15m.
That expenditure was up on the previous term, having surged by 40% since 2011.
It has led to calls for tighter controls on budgets, amid claims that overtime is out of control
Ukip MLA David McNarry said: "It is absolutely deplorable and no-one seems to be doing anything about it."
FIgures obtained by the Belfast Telegraph reveal that in the 12 months to April this year, Stormont departments spent a total of £14.9m on overtime – up 1.5% on 2012/13.
The total number of extra hours worked was 1,024,138. The Department for Social Development had the highest overtime bill – £4.56m for 318,704 extra hours.
The department pointed out, however, that its total included some overtime which was funded by the UK Government. Its Northern Ireland-funded expenditure fell by 16%.
Six other departments saw their overtime bills rise. Some £3.4m was spent by the Department of Agriculture (up 4%) while the Department of the Environment's £1,195,149 outlay rose by 15%.
The Department of Culture, Arts and Leisure (£252,357, up 30%), Department of Education (£174,126, up 53%) and Department for Employment and Learning (£525,302, up 48%) also reported significant rises in overtime spending.
The other body which recorded a rise was the Department of Finance and Personnel, where spending rose by 11% to £2,413,939. The Department of Finance was unable to give a detailed explanation for its increased spending. A spokesperson said: "The department carefully monitors all budgets and expenditure including the use of overtime which requires specific approvals within business areas before it can be undertaken."
Five of the 12 departments had overtime bills running to more than £1m. The Belfast Telegraph has previously reported on the spiralling costs of overtime at Stormont. In 2010/11 a total of £10,663,738 was paid out, but that bill has risen by more than 40%.
Mr McNarry said immediate action must be taken to rein in spending. "There are people queuing up looking for jobs in the Civil Service but they are cutting back on jobs. It makes you wonder if they are cutting back jobs to pay out more for overtime for those who have a job."
Stormont departments are facing increasing pressures on finances. The quarterly budget has been delayed over rows about how to deal with the Treasury's demand for £87m in penalties because welfare reform has not been introduced in Northern Ireland. This is on top of an annual shortfall of around £80m due to spending pressures.
Factfile: Overtime rules
The rules on Civil Service overtime are set out in an 12-page handbook.
It states that hours worked at the request of management, which exceed an employee's conditioned hours, are regarded as overtime.
Staff asked to work overtime between Monday and Saturday are allocated a rate of time and a third. Those who work weekends get a Saturday or Sunday premium. On Saturdays, in addition to time and a third, a payment of half the plain time rate is paid, while on Sundays staff are paid double time.