Stormont's former caretaker ministers made more than £435million of spending decisions in their last eight months in office which senior civil servants refused to endorse.
Fourteen ministerial directions - formal instructions to overrule advice from senior Stormont accounting officers - were issued between February and October, details obtained by Belfast Live show.
It emerges amid warnings of a multi-million-pound "black hole" in Stormont's finances as the UK government moves to set a budget in the absence of a power-sharing Executive.
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Most of the spending, almost £363million, was by the UUP Health Minister Robin Swann via three ministerial directions issued during the period.
Sinn Fein Communities Minister Deirdre Hargey had three ministerial directions for spending decisions worth almost £25million, while DUP Education Minister Michelle McIlveen issued two worth nearly £21million.
The former Justice Minister, Alliance leader Naomi Long, made one ministerial direction for £20million of spending on legal aid.
Former SDLP Infrastructure Minister Nichola Mallon issued two ministerial directions in March worth almost £4million, while DUP Agriculture Minister Edwin Poots issued three worth nearly £4million.
Sinn Fein's Conor Murphy, who was Finance Minister at the time, approved 10 of the ministerial directions, according to the Department of Finance.
He did not approve two ministerial directions by the Health Minister and one by the Communities Minister, while no approval was sought for the Justice Minister's decision.
The Stormont institutions collapsed earlier this year when the DUP withdrew support as part of its protest against Brexit's Northern Ireland Protocol.
Departments have been operating without proper budgets for months.
Civil servants have assumed control of departments after caretaker ministers were removed from office at the end of October when a deadline to restore the Executive passed.
Northern Ireland secretary Chris Heaton-Harris, who is setting a budget in the absence of an Executive, claimed Stormont ministers had "failed to protect the public finances".
He told MPs on Thursday: "Not only did the former Executive fail to agree a budget, but the ministers who remained in their posts during the six months from May to October 2022, left Northern Ireland’s public finances with a black hole of some £660million."
Ministerial directions are issued where a minister decides to continue with a course of action against the advice of their department's accounting officer.
TUV leader Jim Allister said: "It is important to remember that ministerial directions are only issued to overrule civil service advice that expenditure is not value for money."
He said it was "concerning" that the details of ministerial directions were only published following a press query.
The North Antrim MLA added: "This is yet another example of the dysfunctional nature of devolution and how it is simply incapable of delivering the standard of government which is required even on basic issues as transparency on public expenditure.
"At a time when there is huge pressure on finances people will rightly question what is going on."
The five main Stormont parties and the Executive departments were approached for comment.
Asked whether the ministerial directions contributed to the £660million overspend, a Department of Finance spokeswoman said: "The quantum of spend covered by ministerial directions is lower than the forecast overspend.
"It would be for individual departments to say whether the ministerial direction contributed to their forecast overspend."
The UUP said Mr Swann's ministerial directions delivered "key Executive priorities" and he was "not prepared to sacrifice patient health and safety because of political failure at Stormont".
A party spokesman added: "Had those directions not been issued it literally would have cost lives.
“Robin Swann has repeatedly highlighted the impossible position which the health service and its staff were being placed in by the lack of an Executive to other ministers and consistently warned of the dire consequences.
"At all times Robin Swann's priority was to protect vital services, despite the political paralysis in the Executive and Assembly. The Secretary of State could have and should have intervened earlier to address that critical need."
An Alliance spokeswoman said "normal processes were followed" in Mrs Long's ministerial direction, adding: "Legal aid is a vital public service and there are serious implications for access to justice if we cannot afford to provide it."
An SDLP spokesman said: "The only way to properly address concerns around the budget and to ensure the Secretary of State cannot impose harmful revenue-raising measures here is for the DUP to end their boycott of the institutions so that local Ministers can make decisions on behalf of people here.
"The Tories have repeatedly shown that the issues impacting people here are not at the top of their agenda."
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