Amicus was the United Kingdom's second-largest trade union, and the largest private sector union, formed by the merger of Manufacturing Science and Finance, the AEEU (Amalgamated Engineering and Electrical Union) agreed in 2001, and two smaller unions, UNIFI and the GPMU. Amicus also organised in both parts of Ireland and was affiliated to the UK Trades Union Congress, the Irish Congress of Trade Unions and the Scottish Trades Union Congress.