Historically within the party, differentiation was made between the "soft left" and the "hard left", with the former embracing more moderately social democratic views while the hard left subscribed to a strongly socialist, even Marxist, ideology. Members on the hard left were often disparaged as the "loony left," particularly in the popular media. The term "hard left" was sometimes used in the 1980s to describe Trotskyist groups such as the Militant tendency, Socialist Organiser and Socialist Action. In more recent times, Members of Parliament in the Socialist Campaign Group and the Labour Representation Committee are seen as constituting a hard left in contrast to a soft left represented by organisations such as Compass and the magazine Tribune.

What was never used to refer to Trotskyist groups?