Northern Ireland is facing a prolonged period of direct rule from Westminster in the wake of the anticipated collapse of power-sharing at Stormont, a senior Democratic Unionist has predicted.
Jeffrey Donaldson said the bitter political row between his party and its long-term partner in government, Sinn Féin, is unlikely to be resolved without a lengthy talks process following the looming snap election.
The DUP MP also questioned whether the existing mandatory coalition power-sharing arrangements could ever be revived, and said his party could now press for major reform and the introduction of a system of voluntary coalition.
"My own sense of where we are is that we are looking at a prolonged period of direct rule because I don't see these issues being resolved in a talks process in a short space of time," he said.
"I think that Sinn Féin have dealt a serious blow to power-sharing and I think the prospect of a mandatory coalition being restored has been greatly diminished, so if we are going to have another talks process then I think unionists will want to be looking at how Stormont operates and whether we should be moving towards our objective of a voluntary coalition form of government."
If the main unionist and republican parties are returned as the two largest parties after an election, but their row over a renewable heating scandal is still unresolved, along with a range of other political disputes, it is unlikely that a new ruling executive could be formed.
That raises the real prospect of the devolved power-sharing institutions being suspended and a return to direct rule from Westminster.
Emergency legislation would be required in London to enable Northern Ireland Secretary James Brokenshire to put Stormont into cold storage.
Mr Brokenshire will address MPs later on Tuesday after Martin McGuinness's resignation triggered the most serious political crisis at Stormont in a decade.
He will update the House of Commons after t he Sinn Féin Deputy First Minister resigned in protest at the DUP's handling of the botched Renewable Heat Incentive (RHI).
Mr McGuinness's decision to walk away after 10 years of sharing power with the DUP came as First Minister Arlene Foster refused to stand aside to facilitate a probe into the ill-fated RHI - the so-called "cash for ash" furore.
The doomed energy scheme has left the administration in Belfast facing a £490 million bill.
Mr Donaldson claimed observers would be "bewildered" at Sinn Féin's move and said the party had "abandoned" its republican voters.
"At a time when we face enormous decisions about our future, with Brexit and the way this will shape the lives of every single citizen in Northern Ireland for years to come, it is surprising that Sinn Féin have decided to abandon power-sharing and therefore to greatly diminish any influence that they might have over these decisions," he said.
"Sinn Féin don't take their seats at Westminster so they will have no influence there on the decisions that are going to be taken about Brexit and the future of our relationship with the EU and with the Republic of Ireland, whereas the DUP will have enormous influence with our eight seats in a parliament where the government has a small majority."
DUP leader Mrs Foster oversaw the doomed RHI during her time as economy minister. She had repeatedly rejected Sinn Féin's demands to step down temporarily pending the outcome of a preliminary investigation.
Under the structures of the peace process-forged institutions, neither Stormont's First Minister nor Deputy First Minister can remain in post without the other, so Mr McGuinness's resignation spelt the end of Mrs Foster's current tenure in the job.
"We in Sinn Féin will not tolerate the arrogance of Arlene Foster and the DUP," said Mr McGuinness.
"I believe today is the right time to call a halt to the DUP's arrogance."
Mr McGuinness denied that his health problems, for which he is undergoing intensive treatment, had influenced his move.
The state-funded RHI was supposed to offer a proportion of the cost businesses had to pay to run eco-friendly boilers, but the subsidy tariffs were set too high and, without a cap, it ended up paying out significantly more than the price of fuel.
This enabled applicants to "burn to earn" - getting free heat and making a profit as they did so.
Claims of widespread abuse include a farmer allegedly set to pocket around £1 million in the next two decades for heating an empty shed.
While the DUP and Sinn Féin were in agreement on the terms of a potential investigation into RHI, the sticking point was the position of Mrs Foster when the probe got under way.
Steps by the Executive to cut the costs of the overspend will not be implemented in the short term.
Mr McGuinness cited other disputes with the DUP, including over the Irish language and stalled mechanisms to deal with the legacy of the Troubles, in explaining his move.
It is clear that all those issues, and other unresolving rows, would need to be addressed before a new executive could be formed.