The Women's Social Political Union was founded at the Pankhurst family home in Manchester on 10 October 1903 by six women, including Emmeline and Christabel Pankhurst, who soon emerged as the group's leaders. The Women's Social Political Union had split from the less militant National Union of Women's Suffrage Societies, disappointed at the lack of success found by its tactics of lobbying and persuading politicians through meetings.
The founders decided to form a women-only organisation, which would campaign for social reforms, largely in conjunction with the Independent Labour Party. They would also campaign for an extension of women's suffrage, believing that this was central to sexual equality. To illustrate their more militant stance, they adopted the slogan "Deeds, not words". By 1913, the WSPU appointed the fiercely militant feminist Nora Dacre Fox (later known as Norah Elam) as General Secretary. Dacre Fox operated as a highly effective propagandist delivering rousing speeches at the WSPU weekly meetings and writing many of Christabel Pankhurst's speeches.
In 1905, the group convinced the Member of Parliament Bamford Slack to introduce a women's suffrage bill, which was ultimately talked out, but the publicity spurred rapid expansion of the group. The WSPU changed tactics following the failure of the bill; they focused on attacking whichever political party was in government and refused to support any legislation which did not include enfranchisement for women. This translated into abandoning their initial commitment to also supporting immediate social reforms.
In 1906, the group began a series of demonstrations and lobbies of Parliament, leading to the arrest and imprisonment of growing numbers of their members. An attempt to achieve equal franchise gained national attention when an envoy of three hundred women, representing over 125,000 suffragettes argued for women's suffrage with the Prime Minister, Sir Henry Campbell-Bannerman. The Prime Minister agreed with their argument but "was obliged to do nothing at all about it" and so urged the women to "go on pestering" and to exercise "the virtue of patience". Some of the women Campbell-Bannerman advised to be patient had been working for women's rights for as many as fifty years: his advice to "go on pestering" would prove quite unwise. His thoughtless words infuriated the protesters and "by those foolish words the militant movement became irrevocably established, and the stage of revolt began". Commenting on the phenomenon, Charles Hands, writing in the Daily Mail, for the first time described the WSPU's members as suffragettes. In 1907 the organisation held the first of several of their "Women's Parliaments".
The Labour Party then voted to support universal suffrage. This split them from the WSPU, which had always accepted the property qualifications which already applied to women's participation in local elections. Under Christabel's direction, the group began to more explicitly organise exclusively among middle class women, and stated their opposition to all political parties. This led a small group of prominent members to leave and form the Women's Freedom League.