MORE than £20 million was spent by Stormont departments on external consultants between 2011 and last year.
The Department for Social Development (DSD) was by far the biggest spender, forking out almost half the total amount spent by executive departments, at £9.14m.
DSD Minister Maurice Morrow said that 2014/15 had seen a "significant increase due to £4.6 million expenditure in the Social Housing Reform Programme."
The Department of Justice, which spent £1.1m, did reduce its bill dramatically from a high of £529,000 in 2011/12 to just £69,000 last year.
The Department for Regional Development handed over £3m closely followed by the Department of Health, which had a bill of just under £2.5m.
Four departments - Employment and Learning (DEL), Education, Agriculture and Rural Development (DARD), and Culture, Arts and Leisure (DCAL) - spent under £1m in the four year period.
Spending on consultants by DEL increased in every year, trebling from £113,000 in the first year of the 2011 Assembly mandate to almost £360,000 last year.
In addition to the amounts spent on external consultants, DCAL also forked out almost £40,000 in three years on "equality impact assessments and consultations."
In 2010, it was reported that £47m had been spent on consultants in the three years since the Assembly was resurrected in 2007.
The figures, which include amounts for so-called 'arms length bodies', were released in response to an Assembly question by TUV North Antrim MLA Jim Allister, who said he was "disappointed" at the amounts spent.
Three of the Executive's 12 departments, Finance (DFP), OFMDFM and Enterprise, Trade and Investment (DETI), have not yet responded to Mr Allister's request for information.
The TUV leader said: "Stormont departments have spent over £16m of public money on consultants. When the spending of their arm length bodies is included it approaches £20m.
"Considering the array of civil servants employed by these departments I am disappointed that more has not been done to curb this expenditure.
Mr Allister added: "The true figure is not known, because OFMDFM, DFP and DETI have so far ignored the questions asked. What they have to hide I don't know."
