Stormont has rejected the government’s EU withdrawal bill after debating it for the first time since restoring the assembly.
The position was agreed without dissent following a near three-hour debate in Northern Ireland.
It is one of the first substantive acts of business since the Northern Ireland assembly started sitting again just over a week ago.
However the decision will not actually affect Britain’s exit from the EU on 31 January.
Northern Ireland has been unable to speak without the authority of elected ministers throughout most of the debate over Brexit due to the three-year suspension of the devolved institutions.
It comes as Stephen Barclay, the Brexit Secretary, wrote to his counterparts in the Scottish and Welsh governments as they go through the same process.
Mr Barclay told Michael Russell, Scotland’s cabinet secretary for constitutional relations, and Jeremy Miles, the Welsh Brexit minister, that the UK government “should not normally press ahead with legislation without legislative consent motions from devolved administrations”.
But he added that “the circumstances of our departure from the European Union are specific, singular and exceptional”.
“That does not however mean the UK government will not continue to work to address your concerns,” Mr Barclay said.
The Brexit secretary also appeared to chastise his Scottish counterpart for his “public remarks” over the UK government’s consultations.
He said: “The bill was shared with you ahead of introduction and its core provisions have remained consistent over the court of our engagement on this matter since November 2018.”
In Northern Ireland, Jim McAllister, a traditional unionist voice, failed in a bid to delay the assembly debate on Brexit.
He wanted proceedings put back a week in order to allow members to table amendments, but he was voted down.
DUP leader Arlene Foster opened Stormont’s debate and urged the prime minister to “deliver on his promise” of unfettered access to the market in Great Britain.
She said the Brexit deal poses “significant challenges for Northern Ireland” and said members should “take a stand” and show the assembly is “back in business”.
Ahead of the debate, Sinn Fein Deputy First Minister Michelle O’Neill said: “I’m fairly confident the assembly will reject giving consent to Brexit which we all, in the main and in the majority, voted against.
“We are very conscious of the fact – and we have repeatedly stated this – that there is no good to come from Brexit – it brings nothing, only jeopardy to our economy and to jobs, to future prospects, and I think that will be reflected in the debate we will have in assembly chamber today.”
Scottish parliamentarians in Edinburgh have already voted to reject the deal and their Welsh equivalents are likely to do the same.
SDLP leader Colum Eastwood said the government did not care about the people in Northern Ireland, saying: “We have always said people here did not give consent for Brexit and it’s important that this assembly withholds consent for Brexit.
“We know this British government will ignore us but when they are ignoring us they are ignoring the people of Northern Ireland, people of Scotland and the representatives of the people of Wales.
“That shows you what kind of government is sitting now in London. They do not care about people here, they don’t care about people in Scotland, and they are determined to go on with the madness that is this Brexit.”