The Independent Socialist Party (ISP) was a political party in the UK. It was formed in 1934 as a breakaway from the Independent Labour Party (ILP) in protest at the increasing power of the Revolutionary Policy Committee within the ILP. The ISP was socialist and resolutely anti-war, but was firmly anti-communist. It failed to gain substantial support after its formation. Several branches rejoined the ILP during World War II, and, following the deaths of its founders (in 1944 and 1949) the party wound itself up in the early 1950s.