Northern Ireland's deputy first minister Martin McGuinness has resigned from his post in a move that threatens the province's power-sharing agreement.

He said his resignation comes with "deep regret and reluctance" and is in protest at how the Democratic Unionist Party (DUP) dealt with a renewable energy scheme that could see taxpayers footing a bill of over £400m (€461m).

DUP First Minister Arlene Foster had refused to step down and allow the Renewable Heat Incentive (RHI) scheme be investigated, he said.

She presided over the RHI scheme, which intended to subsidise eco-friendly boilers, when she was economy minister, but the subsidy tariffs were not capped – leading to payouts that surpassed the price of fuel.

"It is my firm view that the DUP's handling of this issue has been completely out of step with the public mood, which is rightly outraged at the squandering of public money and the allegations of misconduct and corruption," McGuiness said in his resignation letter.

His resignation, coming into effect at 5pm GMT on Monday (9 January), is likely to lead to a snap election.

The Belfast Telegraph reported that McGuinness's resignation will mean that a collapse of the current administration is inevitable.

McGuinness said that his Sinn Fein party would not seek to replace him in the role, adding: "We now need an election to allow the people to make their own judgment on these issues democratically, at the ballot box".

Power-sharing agreement

Under the terms of the power-sharing agreement, if the post is unfilled, it would trigger the dissolution of 108-member Assembly, which was to govern until the next election in May 2021.

McGuinness said: "Over the last 10 years I have worked with DUP leaders and reached out to unionists on the basis of equality, respect and reconciliation. Over this period the actions of the British government and the DUP have undermined the institutions and eroded public confidence.

"Sinn Fein will not tolerate the arrogance of Arlene Foster and the DUP. There will be no return to the status quo."

On 4 January, Forster said calls for her to step down as First Minister were "misogynistic", telling Sky News that criticism she faced was because "I'm a female, the first female leader of Northern Ireland.

"I've come through a lot worse than venomous attacks from my political opponents and I intend to continue to lead," she told the broadcaster.

The DUP MP Sammy Wilson criticised McGuinness' resignation, saying that it would "deepen" the crisis surrounding the RHI scheme.

"It's in everyone's interests to try and pull back from the brink on this one and find a solution. We have worked very hard to try and achieve that including the offer of a full public inquiry," the BBC reported.