Northern Ireland Secretary of State Theresa Villiers has said she would campaign for the UK to leave the EU.

Ms Villiers is one of six British cabinet members to join the Vote Leave campaign in support of a British exit ahead of the EU referendum on June 23rd.

The referendum follows a deal on renegotiation of UK’s EU membership late on Friday.

UK prime minister David Cameron hailed the landmark deal which gave Britain "special status" in the European Union and pledged to put his "heart and soul" into the campaign to stay in the EU.

Mr Cameron secured endorsement of the EU deal during a meeting with senior ministers on Saturday. He hopes the deal will persuade voters to ratify Britain’s EU membership.

“I will be campaigning with all my heart and soul to persuade the British people to remain in the reformed European Union,” he said after securing the deal that was approved by all the other 27 EU leaders.

“We are stronger, safer and better off inside this reformed European Union,” Mr Cameron said.

Fianna Fáil foreign affairs spokesman Brendan Smith described Ms Villiers's position as worrying. She was entitled to her point of view but "it is clear that a Brexit would be bad for Northern Ireland and bad for Irish-British relations."

In a statement the Cavan-Monaghan TD said the North in particular “has benefitted from the EU’s Peace and Reconciliation fund while agriculture has grown and developed under CAP (Common Agricultural Policy)”.

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”.

Culmination

Minister for Foreign Affairs Charlie Flanagan has welcomed the deal with the UK.

Mr Flanagan said the agreement is “a very significant development”, adding it marks the culmination of several months of negotiations.

Mr Flanagan said the Government is “strongly of the view that the UK should remain in the union”.

“It is now, of course, a matter for the people of the United Kingdom to decide on the future of the UK-EU relationship. While we know from experience that referendums can be challenging, I believe there is now an important opportunity for the people of the United Kingdom to engage on the many positive aspects of EU membership.”

Sinn Féin leader Gerry Adams said he would call on people to vote for Britain to remain in the European Union.

Speaking in Dublin on Saturday, Mr Adams said: “Our decision would be to call upon people to vote to stay in the European Union, notwithstanding our critical position.

“We are critical as a political party of the European Union because of the democratic deficit at the centre and we want to see a more citizen-centred, workers’-rights-centred and a more democratic and social European Union,” said Mr Adams.

“Notwithstanding that, our objection to the British government leaving the European Union is based only upon the fact is that part of this island would be dragged with them if they took that decision and that would have ramifications,” he said.

Minister for Finance Michael Noonan said over the last year the Government had been working with their diplomats to be helpful to the British position.

He said “we have a very strong vested interest in ensuring that Britain remains part of Europe”.

He said Ireland had an influence because “we’re equal partners of 28 countries in Europe”. He said the Taoiseach had been very helpful twice to Mr Cameron over the last few days and did it in the Irish interest, not in the British interest.

Major risks

Mr Noonan said there were major risks to Ireland’s economy if the UK left the EU. However, he was not worried about the free movement of people because “since 1922 we have a united labour market” with the UK.

But there were “other high risks” and a possible exit was a “further risk of instability that must be factored in to how people vote in this election”.

He was speaking on RTÉ radio's Saturday with Claire Byrne programme.

On the same show Fianna Fáil finance spokesman Michael McGrath said given the depth of the trading relations between Ireland and the UK, an exit would be a major risk to Ireland’s economy.

“The strength of the UK economy in recent years insulated Ireland to some extent from a very weak euro zone economy generally because of the amount of trade and exports generally going on across the Irish Sea.”

He said that had been a “very significant boost to the Irish economy and the economic recovery here”.