Sinn Féin TD Pearse Doherty has accused the DUP of "increased arrogance" in the run-up to the resignation of his party's Deputy First Minister in the North, Martin McGuinness.
Echoing statements made by the party's president Gerry Adams on Tuesday, the Sinn Féin finance spokesman said it was "very clear" that the position of DUP First Minister Arlene Foster on the "cash for ash" controversy was not "tenable".
Sinn Féin had demanded that Ms Foster stand aside pending an investigation into the so-called “cash for ash” Renewable Heat Incentive (RHI) scheme, which could result in an overspend of up to £490 million (about €600 million).
The scheme, introduced when Ms Foster was minister for enterprise, was supposed to offer a proportion of the cost businesses had to pay to use eco-friendly boilers, but the subsidy tariffs were set too high.
Without a cap, it ended up paying out significantly more than the price of the fuel.
Mr McGuinness resigned from the position on Monday over Ms Foster’s response to the crisis.
The North faces the prospect of Assembly elections as a result of the resignation, due to the principles of power-sharing.
Speaking to The Irish Times on Tuesday, Mr Doherty said the effect of Mr McGuinness stepping down “has in effect resigned Arlene Foster from the position.
“I think, to be fair, we have given Arlene Foster ample time – this has been going on now for over a month.
“We have asked her privately to step aside without prejudice for a short time until the initial investigation is done. She refused to do so,” said Mr Doherty.
“We asked her to consider that over the Christmas period and Martin again met her privately and asked her to do so.
“So it came to a point that, how can we allow the First Minister to oversee an investigation [of a scheme] where she was the architect, where she was warned about it, which has cost the taxpayer potentially €600 million?”
Mr Doherty said the North’s Executive had now collapsed, as Sinn Féin would not appoint someone to replace Mr McGuinness.
“Given the fact [Ms Foster] was unwilling to step down, we had to take the action of forcing her to step down and we have to allow the public now to have their say,” he said.
‘No going back’
Mr Doherty said Mr McGuinness had made it very clear that the RHI scandal had been a tipping point and there would be “no going back to the status quo.
“We have seen an increased arrogance from the DUP over a period of time and we’ve had scandal after scandal in which they’ve been implicated, including Project Eagle, including the Red Sky scandal.
"We also have the very bigoted decisions that were taken, such as the likes of cutting €50,000 [in allowances for] schoolchildren to attend Irish language college in Donegal and elsewhere, without any consultation.
“We are making it very clear that after an election with a renewed mandate, whatever parties come out from that and in whatever strength they come out from that election, that there has to be a process of negotiations,” Mr Doherty said.
“The Executive will only be re-established, and the DUP will only govern on the basis that they sign up to the principles, and fulfil the principles, of the Good Friday Agreement, which is about equality, which is about respect and which is about parity of esteem.”
Mr Doherty said the peace process was strong and that Sinn Féin would defend it “at all costs”.
Asked about the leadership of Sinn Féin and concerns about the health of Mr McGuinness, Mr Doherty said it was “not an issue that Sinn Féin is fixated about.
“We have very much got a joined-up leadership. We are very much in tune with our grassroots and the key for us is pursuing our objectives, rather than who is the person who sits at the top of the party.”
