Quitting the EU would result in job losses and extra taxes and tariffs, the British chancellor of the exchequer George Osborne warned on a visit to border areas on Monday.
Speaking at Warrenpoint Harbour, Mr Osborne said "agriculture would be particularly hard hit" by Brexit.
Remain campaigners say that agriculture employs 48,000 people in the North and that farmers get 87 per cent of their income from Common Agricultural Policy (CAP) payments.
The chancellor indicated however that the British government would not be able to sustain such levels of support if the UK voted to leave the EU.
“It is not clear that a British government would be able to replicate that. It is not clear that when we were making decisions about where government money went that farmers would get the same as they get at the moment inside the EU,” he said.
Mr Osborne said if people voted to leave the EU, the British government would not be contributing to the EU, but nonetheless the “economy would be poorer”, as less taxes would be raised and there would be less money for public services.
“A chancellor of the exchequer would have to makes choices. With the budget shrinking where are the cuts going to be felt?
“I can’t see why farming would not be excluded from those cuts.”
After meeting business people at Warrenpoint Habour he warned of trade difficulties for both the North and South.
"If we quit the EU, this is going to be the border with the European Union and all the things that those who want to quit the EU claim would happen– ie new immigration checkpoints, border controls and an end to free movement - that has a real consequence.
"There would have be a hardening of the border imposed by the British government or indeed by the Irish Government, " he said.
“That would have an impact on business.”
Referring to the possible consequences of exiting the EU, Mr Osborne said he spoke to a lorry driver in the harbour who remembered “when it used to take two hours to get across the border”.
He said in such resumed circumstances “business would not come here, jobs would not come here, people would trade directly with the Republic”.
Mr Osborne said he had observed Swedish timber being unloaded from a ship onto lorries at the harbour which was destined first for the Republic to be made into timber frames for houses in the North.
In the event of Brexit there would be double taxes, tariffs for the wood coming from Sweden and further tariffs as it was exported to the Republic. Such taxes could result in Warrenpoint losing this business he said.
“All those things have practical consequences. They mean less work for people, more economic insecurity for people, lower incomes for families.
"There is a direct economic cost for people living here in Northern Ireland from quitting the EU."
Mr Osborne said the campaign was “heating up”.
“People know that this is probably the biggest issue we are ever going to be asked to decide as citizens of the United Kingdom,” he added.
Asked to summarise why people in Northern Ireland should vote to remain, he said, "Here we are at the border with the Republic. This would become the border with the European Union if we vote to quit. And that would mean fewer jobs in Northern Ireland, families income hit, it would mean the value of people's homes and their pensions would fall.
“And that is not a price worth paying. Why take this leap in the dark with all the costs and risks associated with it? There is a strong brighter future in a reformed EU if we vote to remain.”
Border trade tariffs
Mr Osborne began his day with an interview with BBC Radio Ulster in Belfast where he suggested Brexit would lead not only to greater Border restrictions but to Border trade tariffs.
“If we quit the EU, what is that border going to look like? Suddenly the Republic is part of the EU, it’s no longer the border between the UK and the Republic of Ireland, it’s the border between the UK and the European Union,” he said.
“The European Union charges a tax, a tariff on things coming into it, which we don’t pay at the minute because we’re in the EU. So who’s going to check what those goods are?”
And he added, “You can’t say ‘we want to have control of our borders’, as they keep claiming, but then say, ‘but it’s not going to have any affect on the borders’. It’s a nonsensical claim by Leave campaigners.”
He was disparaging of Leave arguments that Brexit would not be economically damaging.
“You can’t say you will leave the EU and you will have all of the benefits but none of the costs,” he said.
On immigration and the free movement of people within the EU, Mr Osborne said the freedom of people from Britain and Northern Ireland to travel within the EU would end with Brexit.
“Is the right way to control immigration to wreck our economy? That does not seem to me like a sensible plan for anyone,” he said.
