The ATL executive committee was instructed by its annual conference to boost its 5,500 FE membership. The vote marks a new stage in the war for members with the lecturers' union NATFHE, which dominates the sector with 46,000 members in FE colleges.
Delegates said more FE members had to be involved in the work of the union while college lecturers demanded more publicity of the sector in union literature.
Chris Wilson, a lecturer from Cambridge Regional College, said: "It is not acceptable to think ATL is only for members in schools.
"FE colleagues are 100 per cent committed to ATL as a forward-thinking professional association and trade union, but let's recognise that the ATL is an organisation for all who work in education."