The Electoral Reform Society was founded in January 1884 as the Proportional Representation Society, (the present name was adopted in 1958). The initiative to form the society was taken by Sir John Lubbock (later the first Lord Avebury).  He invited people interested in forming a society for the promotion of proportional representation to attend a meeting. The founding members included academics, barristers and almost equal numbers of Conservative and Liberal MPs; the Labour Party had not then been founded. Among the early members were C.P. Scott, editor of the Manchester Guardian,  Charles Dodgson, better known as Lewis Carroll, and Thomas Hare, regarded as the inventor of the single transferable vote system (STV).

The new organisation examined all the electoral systems which then existed.  The members concluded that the Single Transferable Vote (STV) was the best system and decided to campaign to promote it.  They campaigned for the introduction of STV during consideration of the Reform Bill of 1884 and the Redistribution Bill in 1885. Also in 1885 the Society was asked to help elect the Northumberland Miners' Union Agents, representing the beginning of the Society's work as an independent scrutineer.

The Society was inactive from about 1888 until 1904. When activities were resumed, John Humphreys became first Hon. Secretary, and then full time Secretary until his death in 1946. Intensive campaigning was undertaken during the period before World War I, when the first and only Royal Commission on Electoral Systems was set up. John Humphreys went to South Africa to advise on the electoral system for the new Union of South Africa.

With the formation of local committees under the National Insurance Acts, STV was used for the first time in the United Kingdom.  An amendment to the Third Home Rule Bill saw STV introduced for elections in Ireland, though the Act was suspended on the outbreak of World War I. During the war Humphreys travelled to Australia and New Zealand, visiting Tasmania, which had been using STV since 1907. When the Speaker's Conference on Electoral Reform was set up, he returned to Britain in order to organise the pressure for change. The conference reported in 1917 recommending the STV form of proportional representation.  However,  the proposal was lost when put to the vote in the House of Commons - by just 7 votes. The House of Lords tried to restore STV, but finally only managed to introduce it to elect some of the University MPs.

In 1919, STV was introduced for local elections in the Irish town of Sligo, and in local elections for the whole of Ireland a year later. It was also introduced for the new Parliaments in Dublin and Belfast and also for the directly elected Scottish Educational Authorities.

The early 1920s saw STV adopted by a number of organisations; the Church of England for the Assembly, and numerous educational and professional organisations like the General Dental Council. With four General Elections in 7 years between 1922 and 1929, one might have thought it only a matter of time before Britain changed its electoral system, especially as a number of European countries had adopted proportional voting systems.

However the minority Labour Government introduced an Alternative Vote Bill in 1930, which the House of Lords attempted to amend, but with the fall of the Government in 1931 the bill was lost. The 1931 General Election was the most distorted in British electoral history, but the issue of Proportional Representation in Britain became an academic, rather than a live political issue, and was to remain so for the next 40 years.

During the 1920s supporters included H.G.Wells, Bernard Shaw and Lord Birkenhead, a Conservative Lord Chancellor.

The Second World War and the post-war period represented difficult times for the Electoral Reform Society, especially financially.  During this period, John Humphreys died, John Fitzgerald became Secretary and Miss Enid Lakeman joined the staff as Research Secretary.

The Society's work in acting as returning officers and scrutineer for elections within other organisations, such as trade unions, professional organisations and common interest groups, which had begun before the First World War, expanded greatly. When Major Britton joined the Society's staff in 1965, it became a department in its own right. The Electrical Trades Union ballot rigging case led to the Society being asked to run the elections for the Union. The resulting publicity led to a further expansion of work for other organisations, which improved the Society's standing and finances.

Political interest in reform was boosted by William Whitelaw's decision to re-introduce STV for local elections in Northern Ireland (The Northern Ireland Government had abandoned it during the 1920s). It was further boosted by the February 1974 General Election, when a party with 19% of the vote obtained 2% of the seats and the largest party in terms of votes (Conservatives) was the second party in terms of seats.

In 1983 the Society was recognised by the United Nations Economic and Social Council as a Non Governmental Organisation with Consultative Status.

The Society celebrated its centenary in 1984.  Whereas in 1884 the Single Transferable Vote was not in use in the United Kingdom, today hundreds of organisations use it as their voting system and it is used for most public elections in Northern Ireland.  It is also used for public elections in other parts of the world. The Society continues to press the case for STV for General Elections.

While public interest in voting reform has waxed and waned, in recent years the general trend has been upwards.  In 1990, the Labour Party set up the Plant Commission and in 1992 the then Labour leader John Smith pledged the British people a referendum on the issue.   In December 1997, Tony Blair's Government announced the setting up of the Independent Commission on the Voting System, headed by Lord Jenkins.  The Commission recommend a new system of voting, the Alternative Vote Plus (AV+) to be put to voters against the current system of first-past-the-post.  In its 2001 manifesto, the Labour Party backtracked from its commitment to a referendum, but agreed to hold a review of the voting system.  The Electoral Society is involving itself actively in the campaign to ensure that this review takes place, and that the electorate get to have their say in the final decision.

The creation of devolved bodies for Scotland and Wales in 1999 moved the debate forwards in those countries. While the electoral system used for the new bodies, the Additional Member System, is not ideal, it did mark the recognition that first past the post is not an acceptable system for use in new elected institutions. Devolution has also opened opportunities for further progress, given that the local government electoral system is a devolved responsibility. When the governing coalition in Scotland was renewed in 2003, part of its agreed programme was the introduction of STV for local authorities by the next election in 2007