For many years Labour held to a policy of not allowing residents of Northern Ireland to apply for membership, instead supporting the Social Democratic and Labour Party (SDLP) which informally takes the Labour whip in the House of Commons. The 2003 Labour Party Conference accepted legal advice that the party could not continue to prohibit residents of the province joining, and whilst the National Executive has established a regional constituency party it has not yet agreed to contest elections there. In December 2015 a meeting of the members of the Labour Party in Northern Ireland decided unanimously to contest the elections for the Northern Ireland Assembly held in May 2016.

What party did Labour refuse to support?