The original leadership of the IS (Ireland) left in sympathy with a small tendency in Britian and formed the Irish Workers Group which is now part of the League for the Fifth International and very tiny. Meanwhile IS grew steadily and published a paper called The Worker.
When the Socialist Labour Party was founded in the late 1970s IS joined as a tendency. The Socialist Workers tendency was noted in the SLP for producing a bulletin more professional than that of the party. As the SLP collapsed they left to form the Socialist Workers Movement.
The SWM has gradually grown and has branches in most cities and towns in Ireland and is now known as the Socialist Workers Party. There is no separate SWP in Northern Ireland. There are however branches and members of the SWP of Ireland. Its best known member is Eamonn McCann the radical journalist. In recent years it has suffered two small splits in Belfast and Dublin.