The leader of the DUP has warned the next Prime Minister that the face significant challenges including getting rid of the Northern Ireland Protocol.
Sir Jeffrey Donaldson described the last 24 hours at Westminster as “unprecedented” but insisted that personnel changes in Downing Street do not affect the situation at Stormont.
He said the “foundations of devolved government” are still being “undermined” by the Brexit trading mechanism which “must be replaced”.
“I recognise the efforts made by the outgoing Prime Minister Boris Johnson and his team to replace the Northern Ireland Protocol with arrangements which can command the support of unionists as well as nationalists,” the MP added.
“It is no secret that we believed that Boris Johnson had a duty to get rid of the Irish Sea border having disastrously gone against our advice and signed a Withdrawal Agreement containing the Protocol.
"After two years of failed negotiations, the efforts to remove the Protocol must continue.
“Stable devolved government can only be built on a solid foundation.
"With zero unionist support in the Assembly, the NI Protocol has been undermining the foundations rather than underpinning them.”
Sir Jeffrey acknowledged the leadership of the Conservative and Unionist Party is a matter for members, but reminded them it will affect everyone.
“They should however recognise that no unionist MLAs or MPs support the Protocol,” he said.
"Fully functioning devolved government in Stormont and the Protocol cannot coexist.”
Meanwhile Sinn Fein Vice President Michelle O’Neill has welcomed the end of Boris Johnson’s ‘absurd’ time in charge of the United Kingdom.
The First Minister in waiting was quick to take to social media after the embattled Prime Minister confirmed he intended to resign as Tory Party leader.
“It has been an utter absurdity that the people here have been subjected to Boris Johnson for any length of time,” Ms O’Neill said.
“He is a figure of absolute disrepute.
“Anyone who tries to sabotage our peace agreements, a quarter century of progress and our shared future is truly no friend of ours.”
It followed the Stormont leader’s criticism of former Northern Ireland Secretary Brandon Lewis she accused of "shamefully placated the DUP".
The implosion of Boris Johnson’s premiership has put a question mark over the future of plans to override parts of the Brexit deal.
SDLP leader Colum Eastwood suggested there should now be a General Election.
“Boris Johnson’s government will be remembered for its sleaze, lies, law-breaking and scandal and has trashed relationships across these islands, Europe and America,” he tweeted.
“When he goes, people should be given the chance to end 12 years of Tory misrule.”
Ulster Unionist Party leader Doug Beattie meanwhile said Mr Johnson’s departure has been an “unedifying process which has been of no benefit to anyone”.
"From Brexit to the Protocol, from Partygate to Pincher, it was clear that the Prime Minister`s credibility was fatally damaged and his resignation was therefore inevitable. For the good of the country, he needed to stand down,” Mr Beattie added.
Jim Allister, leader of the TUV, branded Johnson’s time as Prime Minister as “disastrous” for unionism in Northern Ireland.
"With the introduction of the Protocol ensuring that far from securing Brexit for the entire nation, he has left Northern Ireland subject to EU writ and partition from the rest UK,” Mr Allister said.
“With Westminster in state of flux, it is more imperative than ever that unionism holds firm in using Stormont leverage against the iniquitous protocol.”
Former NI Secretary Theresa Villiers says she “would expect” his successor to support the NI Protocol Bill.
“It is absolutely essential that Bill goes through because if the serious political implications it generated in Northern Ireland,” she told BBC Radio Ulster.
“Many of my colleagues feel the same – I would expect all the leadership candidates to back the bill.
“That will be pretty much the first question I ask them.”
Ms Villiers said the next PM must uphold the Good Friday Agreement including Northern Ireland’s status in the United Kingdom.
“It is crucial,” she said.
Meanwhile Baroness Kate Hoey has called on the Government to abandon legislation to stop Troubles related prosecutions by offering a conditional amnesty for those accused of legacy crimes.
“With Brandon Lewis gone, time for the Legacy Bill to be dropped,” she tweeted.
“He was the one pushing it despite virtually no one in Northern Ireland supporting it.”