New DUP leader Jeffrey Donaldson has insisted it is the Northern Ireland Protocol, not his party, which threatens the stability of the Stormont Assembly.
In his first keynote speech since being ratified as leader, Mr Donaldson described the Protocol as the "greatest threat to the economic integrity of the United Kingdom in any of our lifetimes".
He told party members gathered at the Stormont Hotel in east Belfast that the Irish Sea border is "not just a threat to the economic integrity of the United Kingdom", but "a threat to the living standards of the people of Northern Ireland and the constitutional integrity of the United Kingdom".
"In the weeks ahead our goal is to remove the Irish Sea border and to preserve and protect the internal UK market," he said.
Mr Donaldson branded the Protocol a "sledgehammer to crack a nut", describing the trade which passes through Northern Ireland to the EU as "absolutely miniscule in comparison to the trade that the EU does in its entirety".
He said the UK Government should not doubt his party's resolve on the issue.
"This is not the time to talk up a crisis or to unnecessarily raise the temperature, but let me assure you that the Government understands our position and they know what needs to be done," he said.
"I have, in recent days, held a series of meetings on the Protocol, including meetings with the Secretary of State and Lord Frost.
"While the Government is undoubtedly now accepting the case that the Protocol is unsustainable and unacceptable, there is still some way to go to reach an outcome that we can live with."
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Mr Donaldson said the powersharing institutions at Stormont will only work if there is stability across the interlinked relationships between Northern Ireland, Great Britain and the Irish Republic that are set out in peace process agreements.
"The Protocol threatens - not me - the Protocol threatens the stability of the political institutions," he said.
"It is the problem and that problem needs to be resolved."
Mr Donaldson's leadership was rocked on the first day by the resignation of one of his party's Stormont MLAs.
North Down representative Alex Easton, who will now sit as an independent, cited a lack of "respect, discipline or decency" within the DUP as one of the reasons he is quitting.
His move comes after two months of unprecedented internal turmoil for the party.
Bitter divisions within the DUP have been laid bare after successive revolts deposed former leader Arlene Foster and then her successor, Edwin Poots, who quit after just 21 days in the role.
Mr Poots' demise came only weeks after he narrowly defeated Mr Donaldson in the leadership contest to succeed Mrs Foster.
The party's 130-strong executive met at the La Mon Hotel to approve his appointment last night.
Today, Mr Donaldson said he planned to speak with Mr Easton and hoped he would "find his way back to this party".
He paid tribute to the four leaders who preceded him.
He said Mr Poots' tenure may have been short but he had always served the party with "honour and distinction".
Mr Donaldson also apologised for the internal disputes, conceding that events had "strained the patience" of the public and party supporters.
His speech outlined five key priorities for his leadership.
They are removing the "pernicious" Irish Sea border; to make devolution "stable and sustainable"; prioritisation for the health service and economy; to "broaden and deepen" support for Northern Ireland's place in the UK; and to listen to voices right across Northern Ireland.
Mr Donaldson said the next Assembly election will be a "defining moment for Northern Ireland".
"Make no mistake, there are those who will treat next year's Assembly election as a referendum on a border poll that would plunge Northern Ireland into division and instability at a time when we need to be building a stable and united community," he said.
"More than ever, unionists and those who care about peace and stability must come together to resist this threat."
The new leader has made clear his intention to return from Westminster to assume the First Minister's job at Stormont.
However, the timeline for that move remains unclear.
He would have to trigger a parliamentary by-election in Lagan Valley in order to re-enter the Assembly and it is unclear whether he would want to prompt such a contest in the near future, given the DUP's recent poor poll ratings.
He said he will "seek an opportunity to return to the Assembly", either at the next elections due to take place in May 2022, or "there may be an opportunity before that - if it arises I will take that opportunity to return to the Assembly and lead from the front".
Mr Poot's appointee, Paul Givan, remains in place as First Minister.
Mr Donaldson said he plans to talk with his party Assembly members over the next few days to discuss the team at Stormont.
