The Democratic Unionist Party has formally announced its intention to campaign for the UK to exit the European Union.
Party leader Arlene Foster explained the DUP position following Prime Minister David Cameron’s referendum announcement following a deal late on Friday evening.
The three other parties in the Stormont Executive - Sinn Fein, the SDLP and Alliance - all support the UK remaining within the EU.
Northern Ireland Secretary Theresa Villiers has joined a number of her Cabinet colleagues in advocating an EU exit - contrary to the stance taken by Mr Cameron.
The DUP leader said individual members of her party would be free to take opposing sides in the debate but, as a party, they see nothing in this deal that changes our outlook.
Her DUP colleague Sammy Wilson said the EU is “unreformable,” and that its main members want reform in fact they want “even greater political integration” rather than reform.
Over the next months, the British people will be convinced that our future lies outside the EUDUP MP Sammy Wilson
The East Antrim MP added: “Over the next months I believe the British people will be convinced that our future lies outside the EU. We can retain the benefits of access to the EU market without paying billions for the privilege.
“We will be free to make our own deals with growing economies across the world unencumbered by other EU countries’ dictates. We will be able to make our own laws and control who comes into our country. This is a once in a lifetime opportunity we must grasp on referendum day.”
The Ulster Unionist Party, which quit the power-sharing coalition administration in Belfast last year, has yet to officially nail its colours to the mast but said it will “move quickly to a decision” once the “details of any deal were known”.
SDLP leader Colum Eastwood said: “This campaign will be one of the most important votes faced by people in Northern Ireland in decades. It is therefore vital that a strong and positive campaign is conducted to remain in Europe.”
He added: “Secretary of State Theresa Villiers has today joined the Leave Campaign. As I have told her repeatedly, she does not represent Northern Ireland in this position.
“She must not attempt to speak on our behalf. The simple fact is that the pick and mix of extremists and eccentrics in the Leave Campaign have no Plan B.”
Alliance MLA Stewart Dickson said his party appreciates that EU reforms are necessary, but added: “A vote to exit the EU will leave our nation weak and divided. We must vote to stay in so that we can build on the benefits of our membership.”
TUV leader Jim Allister is backing the ‘Brexit’ campaign.
He described the reform deal announced by David Cameron as “pitiful,” and said no powers have been returned to the UK.
“Does it do anything to stop UK laws being subservient to the EU treaties? No. Does it release us from the supremacy of the European Court of Justice? No. Does it do anything to allow us to enter a single trade deal with any country in our own right? No. “Does it do anything to re-establish us as a nation able to control our own destiny? No.”
Mr Allister added: “Roll on the referendum in which TUV will campaign vigorously, and unitedly, and with others to extricate our nation from the EU. We have nothing to lose but our chains.”
Sinn Fein Deputy First Minister Martin McGuinness said the island of Ireland had “benefited greatly” from the EU.
“Benefits of our EU membership can be felt daily across all sections of our society and many organisations and groups have directly benefited from EU funding,” he said.
“In particular, our agriculture and agri-food industry have gone from strength to strength with the help of EU Single Farm Payments.
“The EU has also supported key infrastructure projects and boosted our economy through peace and structural funds. It has also been a key supporter of the progress made in the peace and political processes over the last two decades.”
Meanwhile, Theresa Villiers has said she will vote to leave the EU “to take back control over our country and making our laws and controlling our borders”.
The Northern Ireland Secretary said there were “risks on both sides of this debate” but that leaving was the “safer option”.
Ms Villiers said the UK would then be free to negotiate “a new deal based on free trade and co-operation”.
Minutes after David Cameron announced the date for the referendum, Ms Villiers, along with fellow Cabinet members Michael Gove, Iain Duncan Smith, Chris Grayling, John Whittingdale and Priti Patel made the journey across the river to the headquarters for exit campaign group, Vote Leave.
A total of 16 Cabinet members are backing the Prime Minister’s position that the UK is better off remaining in a reformed EU.
Mr Cameron warned that it would be a “leap in the dark” to leave the European Union as he urged British voters to back his reform deal.
Ms Villiers, who served as an MEP for six years, said she did not believe the EU system was “capable of changing in a way that would be the right option for us”.
Speaking to the BBC, she said: “In the decades ahead we face a European project that is ever more determined to integrate, to take more powers and we could be outvoted many times over the years to come.
“So there is no stable status quo for us to cling to.
“Even with this deal [negotiated with EU leaders by David Cameron] we will still be subject to the Court of European Justice who may still do its best to unpick the deal that’s been agreed.”
In the Republic of Ireland, Fianna Fail foreign affairs and border development spokesman Brendan Smith said Ms Villiers’ position was “wrong for Northern Ireland”.
Mr Smith said: “Brexit would be felt most keenly here in the Republic of Ireland, the only state with a land border to the UK and our biggest trading partner. A UK exit from the EU would create a new wall of regulations from Derry to Down and undo much of the important work on cross-border bodies over the past 18 years.”