The Liberal Party contested no parliamentary elections in Northern Ireland in the inter-war years nor over the period 1945-55. In 1956 the Ulster Liberal Association, later re-named the Ulster Liberal Party, was founded. A limited number of constituencies were contested for both the Westminster and the Stormont Parliaments from 1959. Of the nine candidates listed, three fought elections in constituencies in mainland Britain also, one of whom stood in two regions and another in three.
Shortly after the Westminster General Election of 1970, the Alliance Party of Northern Ireland was founded which absorbed most, but not all, of the membership of the former ULP. A formal relationship existed for over three decades between the Liberal Democratic Party and the APNI when it was termed ‘our sister party.’ This understanding subsequently lapsed. The first APNI MP elected to the House of Commons, Naomi Long, for Belfast East in 2010, did not take the Lib Dem whip and moreover sat on the opposition benches throughout the Coalition government 2010-15, expressing disagreement with key policies which appeared in the Liberal Democratic Party Manifesto at the 2010 General Election.