David Cameron has warned voters in Northern Ireland of the potential economic impact of Brexit as he continues a tour of the UK setting out the case for staying in the European Union.
The PM said the country's economy and farming industry were too closely linked to the EU to risk the "leap in the dark" of voting to quit the 28-nation bloc.
Northern Ireland's political parties are split on the issue, with the Democratic Unionists backing "leave" and Sinn Fein, the SDLP and the cross-community Alliance Party in favour of "remain".
A declaration is expected next week from the Ulster Unionists.
Northern Ireland Secretary Theresa Villiers is one of five cabinet ministers who have broken ranks to campaign for the UK to end ties with Brussels.
Speaking ahead of the latest leg of his tour, Mr Cameron said: "I'm clear that the people of Northern Ireland, and the whole UK, are better off in a reformed European Union.
"More than 60% of Northern Ireland's exports go to the EU, and around 40% of its investment comes from the EU. Putting that at risk is a leap in the dark."
"It's vital that the voices of Northern Ireland's farmers are heard in this debate.
"They want security and certainty. I've never argued the EU is perfect, but I believe a reformed Europe gives them access to a huge single market and an income that helps them keep food prices low for families.
"Those who want the UK to leave the EU need to give answers on their alternatives."
Treasury figures put the number of jobs in Northern Ireland linked to EU trade at 50,000 in Northern Ireland, with exports up over 50% in real terms since 1998.