Northern Ireland farmers could face huge cuts to their subsidies if the public votes for a Brexit, George Osborne warned yesterday.
On a visit to Warrenpoint, the Chancellor said the Government would likely be unable to match the £2bn the EU gives the industry over a seven-year period.
"What would happen if we left?" he asked. "The country would have less money. A Chancellor of the Exchequer would have to make choices.
"The budget would shrink, and where are the cuts going to be felt? I cannot see why farming would be excluded from those cuts."
Mr Osborne also warned that border controls between Northern Ireland and the Republic could be reintroduced if the public voted for Leave.
Speaking to the Press ahead of a tour of Warrenpoint Harbour the Chancellor, who previously warned a Brexit would trigger a "profound economic shock", said pulling out would lead to an inevitable toughening of controls between North and South.
"I'm here at Warrenpoint, and this place is a very practical demonstration of the fact that Northern Ireland has the only land border with an EU country," he added.
"If we were to quit the EU, then jobs would be lost. I think that Northern Ireland would be particularly hard-hit. You would have a hardening of the border.
"You only have to listen to the businesses at the port here telling us that jobs would be lost and their futures would be uncertain."
Mr Osborne claimed that a Brexit would mean "fewer jobs in Northern Ireland, family incomes hit" and the value of properties falling.
He described it as "not a price worth paying".
"We've come a long way from the mess the country was in, economically, seven or eight years ago. We don't want to go back to square one," he said.
"If we quit the European Union, then this is going to be the border with the European Union.
"There would have to be a hardening of the border that would be imposed by the British Government or, indeed, by the Irish Government, and that would then have an impact on business."
Mr Osborne told how one of the drivers at Warrenpoint Harbour had described two-hour queues to enter the Republic when there were border controls, and said that no one wanted to see that again.
"Business wouldn't come here, jobs wouldn't come here and people would trade directly with the Republic," he added.
It was also claimed farmers and milk producers hoping to sell their goods in the Republic would be hit with tariffs.
"If you are trying to sell from outside of the EU into the EU, you have to pay tax," Mr Osborne said."That would hit farmers' incomes here.
"Farmers also get support from the Common Agriculture Policy. It's not clear that a British Government would be able to replicate that. I think agriculture would be particularly hard-hit."
Warrenpoint Harbour handles more than three million tonnes of cargo every year.
It deals with a range of industry imports and exports, with vast piles of wood stacked in and around the estate.
It also handles a huge volume of cement exports, and recently started building work on a £2.5m expansion with Quinn Cement.