The Supreme Court ruling that Ministers do not need to ask permission from Northern Ireland before triggering Article 50 'undermines the democratic mandate of our Assembly", the SDLP have said.
Top lawyers, including Northern Ireland's Attorney General, had locked horns in the Supreme Court over whether Government ministers can use the royal prerogative to commence the UK's withdrawal from the EU.
On Tuesday the highest court in the land rejected an appeal by ministers against a High Court judgment blocking their decision to begin Britain's exit from the European Union without Parliament having a say. It means Parliament must vote on legislation to trigger Brexit.
The court ruled the Scottish Parliament, Welsh and Northern Ireland assemblies did not need a say.
Northern Ireland voted to Remain in the EU by a margin of 56 per cent.
SDLP leader Colum Eastwood said: “Northern Ireland voted to remain in the European Union, yet the Northern Ireland Assembly is being denied any role or rights in the upcoming negotiations with the European Union.
“The SDLP is now the only party standing by the will of the majority of people in Northern Ireland at Westminster. We will be the only voice of the 56% who voted remain.
He added: “I welcome the part of the judgement which ensures that a vote in Westminster will be required to give consent on the triggering of Article 50. We will submit our own amendments and support any other amendments which protect our interests. We will vote against any Bill which triggers Article 50. I would strongly urge all pro-Remain MPs to join us in this action."
Sinn Fein's Gerry Adams warned that Brexit "will undermine the institutional, constitutional and legal integrity of the Good Friday Agreement".
He said: "It puts the British Government on a collision course with the EU in which our stability and economic progress are regarded as collateral damage.
"The Taoiseach and the Irish government must uphold the Remain vote in the North. And to argue for the North to be accorded a special designated status within the EU."
Ulster Unionist MPs, Tom Elliott and Danny Kinahan said the challenge now is to find the best deal for Northern Ireland.
“On the 23rd June the people of the United Kingdom voted to leave the European Union and on that basis, our MPs will be voting to trigger Article 50 when the vote comes to Parliament.
“We welcome that the Supreme Court has noted that the devolved administrations will not have a veto on the UK’s decision to withdraw from the EU.
“We joined the European Economic Community as one United Kingdom, and we will leave the European Union as one United Kingdom.
“The challenge now is to secure the best deal for Northern Ireland. It is clear that the failed DUP/Sinn Fein Executive, which has crumbled after 8 months, is incapable of addressing Northern Ireland’s unique needs in Brexit negotiations."
DUP MP Sammy Wilson said: "We will be using our votes and voice to ensure a rapid commencement on the negotiations to leave the EU, completely as the Prime Minister promised."
He said the party will ensure "that the issues most concerning to Northern Ireland are articulated by our MPs".
Mr Wilson added: "It would have been totally irrational to have the Northern Ireland Assembly, Welsh Assembly and Scottish Parliament dictate the direction in which the nation should go after such a clear and decisive vote.
Alliance MLA David Ford welcomed the ruling but said he was disappointed the devolved institutions will not be consulted on the Brexit process.
“The decision the three devolved assemblies do not need to be consulted does raise significant issues for the future of devolution across the UK, on a wide range of issues and not just membership of the EU. In the longer term, this is likely to create significant debate in all three.
“Brexit has such fundamental implications for the wider UK and specifically Northern Ireland, it would have been an affront to democracy to if the formal triggering of Article 50 was not subject to detailed scrutiny and accountability by Parliament.”