The first minister is facing fresh calls to resign after it was revealed she wrote to banks encouraging support for the bugled Renewable Heat Incentive scheme.
In a letter to Northern Ireland’s leading banks written when the scheme was first set up, Arlene Foster - who was then enterprise minister – reassured bankers that payments would be guaranteed.
She added that the uptake of the scheme was dependent in many cases on people obtaining loans, stating: “I am therefore writing to encourage you to look favourably on approaches from businesses that are seeking finance to install renewable technologies.
“The government support, on offer throughout the incentive schemes, is reliable, long term and offers a good return on investment.”
Fatal errors in how the RHI scheme was set up have left Stormont facing a potential £490 million overspend bill over the next two decades.
In the wake of the latest revelations over the RHI fiasco, some of Mrs Foster’s political rivals have renewed calls for the First Minister to step aside while a public enquiry is carried out.
Ulster Unionist leader Mike Nesbitt and the SDLP’s Colum Eastwood are among opposition MLAs seeking Mrs Foster’s resignation.
Mr Nesbitt said: “As every day passes, further information emerges regarding Mrs Foster’s central role in what she herself told the Northern Ireland Assembly was the ‘debacle’ of the Renewable Heat Incentive she introduced during her time in the Department of Enterprise, Trade & Investment.
“It is now clear she was warned in advance that there was a danger of ‘over incentivising’ the scheme, the very error she endorsed as Energy Minister.
“Once again, with no pleasure, I ask Mrs Foster to prioritise the future of the Stormont institutions over her role within them and resign. She knows it is the right thing to do for Northern Ireland.”
SDLP leader Mr Eastwood said the First Minister has “lost the confidence of the Assembly and of the public”.
He added: “ As further information comes to light relating to her specific knowledge about the detail and scale of the RHI scheme, the pretence that she was not across every ‘jot and tittle’ has lost all credibility.
“If Arlene Foster has done nothing wrong, as she claims, then she has nothing to fear from a public inquiry with full powers to compel witnesses and evidence.
“All parties, and particularly Sinn Féin, must now clearly put on record their support for such an inquiry to uncover the truth about this fiasco.
“I am again urging the First Minister - abide by the will of the Assembly. Listen to the will of the public. Stand aside and begin to restore faith in our institutions.”
TUV leader Jim Allister said the letters indicate “a far greater ministerial attachment” to the RHI than had been acknowledged before.
He also said that, since they contain assurances that the Government was guaranteeing the scheme, they might make it harder to find a way of cutting down on the ultimate cost which the scheme will spell for Northern Irish taxpayers.
The DUP leader has remained defiant throughout the scandal and refused to step aside, claiming that Stormont will be able to claw back millions of pounds which have been committed to the botched RHI scheme.