They had several major disagreements with the IS leadership, including what they perceived as an increasingly ultra left stance, refusing to work with other socialist groups, and a reduction in internal democracy.
Following this a considerable number of IS members left the group including the influential engineering fraction in Birmingham.
A large number of former IS members, but crucially not all the ISO's leaders including Roger Protz and John Palmer, then regrouped around Jim Higgins to form the Workers' League basing themselves on what they described as the IS tradition with an orientation on rank and file work in the workplaces and unions which they alleged IS had abandoned.
A conference on Revolutionary Unity and the International Socialist tradition was organised by Martin Shaw, who was not a member of the WL, after which the group seems to have dissolved itself.
The remaining members joined various groups including Big Flame and the IMG or simply dropped out of organised revolutionary politics.