Prime Minister David Cameron has been in Northern Ireland as part of his UK tour to persuade voters that membership of a reformed EU is in their best interests.
Mr Cameron visited two businesses in County Antrim.
His first stop was at the Bushmills whiskey distillery. He then travelled to a farm in Ahoghill.
Northern Ireland farming relies heavily on EU subsidies and Mr Cameron said leaving the EU would be a huge risk.
"I would say it comes down to a very simple argument, which is do we want a greater United Kingdom inside the European Union with the safety, the strength and the prosperity?" he said.
"Or do we want a great leap in the dark?
"And I think particularly when it comes to farming you know what we have today - you know about the market access, you know about what we can do and we could be putting all that at risk which I think would be very, very damaging for Britain's farmers and for farmers here in Northern Ireland."
Mr Cameron also said that if the UK left the European Union, current arrangements at the Irish border could be affected.
"It's for the people who want us to leave who need to answer these questions," he said.
"Are they going to put in place harder border arrangements between Northern Ireland and the Republic? What would queues be like, how long would it take people to get across the border? Is that what they're contemplating?"
London Mayor Boris Johnson, who is campaigning to leave the EU, will visit Northern Ireland on Monday.
Mr Johnson is one of the most high-profile politicians campaigning for Britain to leave the EU.
In the Times on Saturday he said the vote was a golden opportunity to "take back control, to renew our approach to law making, to strike new trade deals around the world, to galvanise our economy and politics and to give people confidence back in their country."
Northern Ireland Secretary Theresa Villiers has previously announced she will vote to leave the EU, describing it as the "safer option".
She says her vote would be "to take back control over our country and making our laws and controlling our borders".