 The union was formed as the National Amalgamated Coal Porters Union of Inland and Seaborne Coal Workers in 1890, and affiliated with the Trades Union Congress in 1890.Union membership grew rapidly from 5000 in 1891 to 12,000 in 1892.A major three-week strike occurred in London in 1892, involving 6,000 members of the union, over the employment on a non-union worker and the failure of some employers to pay standard wages.