Arlene Foster with David McIlveen pictured during last Mays Assembly election campaign

Writing in Thursday’s News Letter, former North Antrim MLA David McIlveen says that Mrs Foster has “seriously misjudged the public anger” over a debacle which could cost taxpayers around half a billion pounds.

In an exceptionally blunt public critique of Mrs Foster’s actions, Mr McIlveen said that “without doubt” the words “electoral liability” are now heard within the DUP in relation to a “deeply damaged” Mrs Foster who he said is unlikely to lead the DUP into the next scheduled election.

Mr McIlveen, who was Assembly private secretary to finance minister Simon Hamilton in the last Assembly before losing out to party colleague Phillip Logan in last May’s election, said that Mrs Foster’s lack of humility had turned the RHI situation into a “crisis”.

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The former MLA, who is the son of the Rev David McIlveen, the Free Presbyterian minister and close friend of DUP founder Ian Paisley, said that his leader had demonstrated a “lack of maturity” by choosing to make a “knee-jerk reaction” to colleague Jonathan Bell’s allegations about the scheme.

DUP members on various wings of the party who have spoken privately to the News Letter over recent days have suggested that although there is deep internal alarm over the RHI scandal, Mrs Foster is not in any imminent danger of being forced out.

But Mr McIlveen set out a different opinion: “Whilst the view in public is that ‘Arlene’s team’ are as loyal and happy as ever, the reality in private is something very different.”

He said that in private elected representatives concede that another election campaign framed around Mrs Foster would now be impossible.

In unusually candid comments from a DUP member about the inner workings of Northern Ireland’s dominant party, Mr McIlveen said that more than any other party the DUP is “obsessed with elections” and every decision is scrutinised in light of how it might play with voters.

For that reason, he said that the RHI debacle was “likely driven more by a mixture of ineptitude and a desire to curry favour with the rural electorate rather than by something more sinister”.

Responding to the article, a DUP spokesman said: “Former MLA David McIlveen is entitled to his personal opinions, however this is the first time that he has articulated any view since losing his seat.