"No compelling argument" has been made that Northern Ireland's agriculture industry would be better off if the UK left the European Union, the Ulster Farmers' Union (UFU) has said.
Farmers in Northern Ireland receive more than £230m a year in subsidies from the EU, which the UFU says is "vital" for farm incomes.
A referendum on whether the UK should stay in the EU will be held on 23 June.
The UFU said "future financial support is the central issue" in the debate.
Ian Marshall, the union's president, said "no alternative support measures have been put forward" by those pressing for the UK to leave the EU.
"In addition, the EU is our biggest export market, and we would need firm assurances about access to that market, should the UK vote to leave," he said.
Mr Marshall said both sides in the debate needed to set out their vision of the future for agriculture, but added that "our view for now is it will fare better in the EU".
But he said the union would not be telling its members how they should vote.
Earlier this week, Democratic Unionist Party MP Gavin Robinson suggested farmers could get a more generous subsidy outside the EU.
And on Monday, his party's deputy leader, Nigel Dodds, said the EU's focus "is moving away from food production".
"The idea that somehow there's a great guarantee for anyone in terms of the current status quo in Europe is wrong," he added.