The Ulster Unionist Party has declared itself on the remain side of the EU referendum debate.
The UUP was the last main party in Northern Ireland to state its official position.
Sinn Fein, the SDLP and Alliance party are also campaigning for the UK to stay in the EU, though t he Democratic Unionists are recommending voters back a Brexit.
The move by the UUP means the debate in Northern Ireland will not divide along traditional orange/green lines.
The party announcement came after a meeting of its ruling executive. It said party members would be free to vote either way in June's referendum.
A UUP spokesman said: "The following motion was passed today by the Ulster Unionist Party Executive: "The Ulster Unionist Party believes that on balance Northern Ireland is better remaining in the European Union, with the UK Government pressing for further reform and a return to the founding principle of free trade, not greater political union. The Party respects that individual members may vote for withdrawal on the 23rd of June."