Whereas the dramatic struggle for the suffrage has received extensive academic attention the feminist campaigns that came immediately after 1918 have been largely ignored. This thesis argues that there was vigorous grassroots feminist activity in the inter-war years which can be seen in the activities of the Society for the Promotion of Birth Control Clinics (SPBCC) who in the post-suffrage era explored their new opportunities. Themes running through this thesis include feminism, grassroots activity, locality and modernism. This research utilises the theoretical framework of comparative social movement theory as well as historical research. A Collective Biography of SPBCC committee members has been constructed to give a profile of activists. This thesis argues that the debate within the post-suffrage society the National Union of Societies for Equal Citizenship gave backing to the new feminist master frame which emphasised women's role as mothers. This strengthened the SPBCC which campaigned to give working class mothers the knowledge to limit their families, something available privately to middle class mothers. This research explores how the SPBCC tried to pursue its case by creating alliances with the National Council of Women and the Women's Citizenship Association,This study shows how local SPBCC groups attempted to prove the need for birth control clinics by mobilising and founding clinics. Middle class women played an important part in this direct action, but working class women, either individually or from the Women's Cooperative Guilds also participated. Class differences were important, but this research shows that volunteers, who were all mothers themselves, stressed the common bond of motherhood. The SPBCC both locally and nationally strove to counter the condemnation of the medical profession and the Churches. The interplay of religious and political forces is seen in case studies in Stockport, Glasgow, Manchester and Salford, Liverpool. The thesis compares the birth control strategies of the confrontational birth control pioneer Marie Stopes with the more analytical approach of Eleanor Rathbone of NUSEC. This research reveals that some SPBCC members felt they had to make uncomfortable choices between class and gender allegiances or feminism and eugenics. This thesis demonstrates how the SPBCC tested the new political structures by attempting to place birth control on the agenda of national political parties, particularly the Labour Party. However, there was more success in building birth control policy advocacy coalitions at the local level. In 1931 the Labour Government issued Memorandum 153/MCW which allowed municipal clinics to provide birth control advice but this thesis questions to what extent this was a victory. Arguably the SPBCC did not achieve its main objective but it did empower its feminist members in a wide range of political activities.