Civil service chief David Sterling believed Sinn Féin minister Máirtín Ó Muilleoir 'may be acting under instruction'
The head of the Northern Ireland civil service has said that the role of Stormont's special advisers should be reviewed, with ministers made aware that they are fully responsible for their Spads actions before there is any return to Stormont.
David Sterling's comments are contained in witness statements to the Renewable Heat Incentive (RHI) inquiry, which he will deliver in person later today.
They come as further evidence has been published pointing to the role unelected party advisers played in ministerial decision making prior to the collapse of the assembly in January 2017.
Earlier this week the inquiry, chaired by retired judge Sir Patrick Coghlin, heard from former Sinn Féin finance minister Máirtín Ó Muilleoir whom written evidence showed was emailing backroom party figures, including Ted Howell, a close confidant of Gerry Adams and senior republican Pádraic Wilson, to discuss the party's decision making in relation to RHI.
Further evidence published last night ahead of Mr Sterling giving his final evidence shows that civil servants believed Mr Ó Muilleoir was "acting under instruction".
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In a text message exchange between the senior civil servant and former permanent secretary Dr Andrew McCormick, discussing a proposed business plan to try and mitigate the RHI losses, Mr Sterling says that he has been in touch with Mr Ó Muilleoir but added he was "unforthcoming".
"I can't say whether the will is there and wonder whether he knows himself. He may be acting under instruction".
Mr Sterling has led the civil service at Stormont since June 2017. He was previously the permanent secretary in the enterprise and finance departments.
While the inquiry is focusing on the background to the RHI scandal it has also touched on the role unelected special advisers played in making major decisions.
Mr Sterling's latest evidence to the inquiry states that he believes there is a "strong case" for a review of the role of advisers before any return to devolution and that it should be made clear to ministers that they are "fully responsible and accountable for them".
The inquiry has heard that DUP advisers took major decisions and in many cases were believed to wield more power than the ministers they were meant to be advising.
Mr Sterling said the civil service would be in a position to make recommendations to any future ministers.
Dr Andrew McCormick, will also return to finish his evidence to the inquiry today. Oral hearings are due to end tomorrow, after 111 days of evidence heard by the panel.