The following account is taken from The Electoral System in Britain Since 1918 by D.E. Butler, Oxford University Press, 1963.
The Speaker's Conference on Electoral Reform which reported in January 1917 unanimously advocated proportional representation (PR) in the form of the single transferable vote in constituencies returning from three to seven members. But in June 1917 the House of Commons voted by a majority of eight (149 votes to 141) that the Boundary Commissioners should work on the assumption that PR would not be enacted. The division of the parties was as follows:
Conservative: 38 for PR, 85 against.
Liberal: 77 for, 54 against.
Labour: 12 for, 10 against.
Irish Nationalists: 14 for, none against.
In August 1917, on the committee stage of the Representation of the People Bill, PR was defeated by a majority of 32 votes, and the alternative vote (AV) was substituted by a majority of one (127 votes to 126). The parties divided as follows:
Conservative: 2 for AV, 113 against.
Liberal: 98 for, 13 against.
Labour: 17 for, none against.
Irish Nationalists: 10 for, none against.
When the Bill was debated in the House of Lords, the alternative vote was struck out and PR substituted in its place. "The House of Commons rejected the Lords' amendments by 223 votes to 113 and then by 178 votes to 170 reinstated the alternative vote. The House of Lords insisted on their amendments, although they retreated from complete to partial P.R. The House of Commons again rejected P.R. (this time by 238-141) and once more by a majority of one vote (195-194) insisted upon the alternative vote. Finally in the last hours of the session, a compromise was arranged. The alternative vote was abandoned and the Boundary Commissioners were instructed to prepare a limited scheme of P.R. to apply to 100 seats."
"When the Boundary Commission produced the scheme, it was rejected by the House of Commons. Hardly any members in the areas affected by it supported it."
Although the Commons voted three times for the alternative vote by very narrow majorities, they voted against PR three times, twice by large majorities. The average of the votes was: For PR/alternative vote 149, against 183.
In February 1931 during the Labour government of Ramsay MacDonald which was dependent on Liberal support, the Electoral Reform Bill which provided for the use of the alternative vote, received a second reading in the House of Commons by a majority of 295 votes to 230 on a strict party division.
In June 1931, the House of Lords gave the Bill a second reading by
50 votes ro 14. In the committee stage an amendment was passed by 80 votes to 29 to limit the application of the alternative vote to constituencies in boroughs which had a population of more than 200,000. One hundred and seventy-four constituencies fell into this category. The amended Bill received its third reading on 21 July and was returned to the Commons.
The government decided not to consider the Lords' amendments until the autumn. However the government fell in August, and a National Government took its place. No more was heard about the Bill in public.
The adoption of the single transferable vote or the alternative vote in 1918 would undoubtedly have benefitted the Liberal Party, and harmed the Conservative Party. Its effect on the electoral fortunes of the Labour Party would have been mixed.