The SWP initially grew from a grouping in the Labour Party around the Socialist Review publication. This was a regroupment of Tony Cliff's after some were expelled from the Gerry Healy led Labour Party entrist group called The Club. Cliff's supporters had previously been members of the Revolutionary Communist Party.
Although technically expelled for breach of discipline, in a Birmingham Trades Council vote, on the issue of the war in Korea the actual cause of the dispute was Yugoslavia and behind that the class nature of the Russian state. Trotskyism after World War Two was faced with the problem of analysing the class nature of the 'glacis states', as they called them, of Eastern Europe. Initially they were described as state capitalist bonapartist formations in which the Stalinist parties held power. But as time went by the Fourth International decided that they were to be described as being deformed workers states analogous to the Russian degenerated workers state. The latter position being that of Leon Trotsky.
However Tony Cliff's view was different and he analysed the Russian state as being bureaucratic state capitalist too. This represented a major breach with the conservative views of the Fourth International's majority and brough him into conflict with them. So when the FI leadership became sympathetic to Tito's Yugoslavia the RCP in Britain was hostile to their views and Cliff most of all. But the RCP leadership collapsed in the course of the ensuing debate with many of its central cadre leaving politics and others, such as Ted Grant, failing to defend their views, as he has recently pointed out. This left Cliff as the most outspoken critic of the FI and its British supporters around Gerry Healy hence the expulsion of Cliff's supporters. Cliff himself could not be expelled however not being subject to the leadership of The Club as an exile in Dublin.
When organised around the new journal Socialist Review Cliff's supporters thought of themselves as being a Trotskyist tendency differning from the majority of Trotskyists only in their view of the Stalinist states being what they described as state bureaucratic capitalist. This theory, usually abbreviated to state capitalism, has been a hallmark of the tendency ever since. Readers should also note that this theory of state capitalism needs to be differentiated from previous theories such as that of Lenin. Cliff's theory being intended to describe the political economy of the Stalinist states is normative and does not in itself seek to describe state capitalism as a general tedency within capitalism. Later writers however building on Cliff's work did however develop this latent side of Cliff's analysis of Stalinism. For example readers are refered to the work of Michael Kidron and Nigel Harris.
In 1962 the Socialist Review Group became the International Socialists after the name of their new journal first published in 1960. They also began publishing a paper called Industrial Worker which was later renamed Labour Worker. This was the forerunner of Socialist Worker which was launched in 1968 with Roger Protz as editor.
The organisation is part of the Trotskyist movement, which includes several other British parties, such as the Socialist Party of England and Wales, the Alliance for Workers Liberty and Workers Power (an old political joke in the UK refers to the various factions around its left-wing fringes as the 57 varieties of socialism, a reference to a famous advertising slogan employed by baked bean manufacturers Heinz).
The SWP's theoreticians developed three major theories, which moved them away from the official Trotskyist movement:
Increasing problems in the mid-1970s and a failure to recruit led to disputes within the leadership of IS. The eventual result was that a large section of the leadership, in paticular Jim Higgins, Roger Protz and John Palmer, were expelled in 1975 and formed the emphemeral Workers League. Soon after the IS ditched their commitment to building a rank and file movement in practice and in 1977 launched the SWP.
Soon after becoming the SWP it launched the Anti Nazi League in response to the perceived danger of the National Front. The ANL followed on from the relative success of the Right to Work Campaign which had been launched as the dying effort of the National Rank and File Orgnising Committee and had organised a series of marches against unemployment. These marches were annual events between 1976 and 1981. However the ANL was far larger than the RTWC and able to call upon support far outside the ranks of the SWP which retained organisational control. In its own terms the ANL was relatively successful holding a series of large demonstartions against the NF and was to some considerable degree respoponsible for the marginalisation of that grouping. By 1981 it was felt to be no longer needed and was then dissolved.
The SWP has a reputation for throwing itself into various campaigns, ranging from the Anti Nazi League and Rock Against Racism, to the anti-capitalist movement and the Socialist Alliance to the Stop the War Coalition. Critics have accused some of these like the Anti Nazi League and Globalise Resistance are no more than fronts for the party, intended to recruit new members while pretending to be broad organisations.
In Scotland SWP members joined the Scottish Socialist Party as an officially recognised faction in 2001. They are therefore known as the Socialist Worker Platform and distribute the publications of the state-wide SWP only within the ranks of the SSP being prohibited from doing so publically. A number of Socilist Worker Platform members are on the National Committee of the SWP at a state-wide level which illustrates the nature of the relationship.