First Minister Paul Givan has confirmed his resignation, saying holding the post at Stormont has been the "privilege of my life'.
The move comes a day after his party colleague Edwin Poots’ decision to order a halt to agri-food checks at Northern Ireland’s ports.
DUP leader Sir Jeffrey Donaldson has repeatedly threatened to bring down the Stormont institutions in protest against the so-called Irish Sea border, introduced as part of the post- Brexit protocol.
Mr Givan's statement followed a meeting of senior DUP figures at a Belfast hotel on Thursday afternoon.
The Lagan Valley MLA, who only took on the role of First Minister in June 2021, said: “Today marks the end of what has been the privilege of my lifetime – to serve as the First Minister of Northern Ireland.
“When I first entered the Assembly 12 years ago, I never expected to have the opportunity to lead the Government and serve the people of Northern Ireland as First Minister.
“Holding this office is one that comes with a heavy responsibility and I have often felt the weight of this burden, to do what is right for all out people.”
He also thanked Edwin Poots for nominating him for the role, Sir Jeffrey Donaldson for asking him to continue in the job and his family for their support during his time in office.
Sir Jeffrey Donaldson said his party has focused minds on tackling issues with the Northern Ireland Protocol.
"We have reminded the Government of their promise in the New Decade, New Approach agreement to protect Northern Ireland's place within the UK internal market," he said.
"This commitment was the basis upon which we re-entered the Executive in early 2020 and have participated in the political institutions since then. To date, this commitment has not been honoured by the UK Government."
Mr Givan's resignation as First Minister automatically removes Sinn Fein deputy First Minister Michelle O’Neill from office.
Ahead of the official announcement, Sinn Fein leader Mary Lou McDonald called for an early election at Stormont.
Ms McDonald said: "I want to be clear, we cannot stagger on in the months ahead without a functioning executive. Sinn Fein will not facilitate this.
"So in the absence of a functioning executive, an early election must be called and the people must have their say."
The expected resignation of Paul Givan has also sparked criticism from other parties across the divide at Stormont.
SDLP leader Colum Eastwood and deputy leader Nichola Mallon said they have written to Prime Minister Boris Johnson over the latest threat to devolved government at Stormont, which they described as a "gross betrayal of people in Northern Ireland".
The Foyle MP said: "Whatever community you're from, whatever your background or beliefs, no-one benefits from this cynical, and totally predictable, electioneering stunt."
UUP leader Doug Beattie blasted what he called "another manufactured crisis", saying it will have one effect - the instability of Northern Ireland and people will suffer.
"They have suffered enough and they are going to suffer more. They will suffer in the medium term and they will suffer in the long term and all politicians should be standing here and everything that they do they should be doing for the betterment of the people of Northern Ireland," he said.
Other ministers in the Stormont administration can still remain in place however, the Executive cannot make any significant decisions including agreeing a three-year budget - a spending plan that is currently out for public consultation.
Meanwhile, a planned official state apology by Mr Givan and Ms O'Neill to victims of historic institutional abuse, scheduled for March, will also not happen.
A number of Covid-19 restrictions remain in place in Northern Ireland and their status in the event of an Executive collapse remains unclear.
