The 1930s and the British labour movement: chronology
Dates and statistics, 1929 to 1945. 30 May 1929 Labour wins the general election with Ramsay Macdonald as prime minister. TUC affiliated membership is 3.7 million - down from 4.2 million in 1926, 4.4 million in 1922, and 6.5 million in 1919-20. Labour Party membership rises steadily from 215,000 in 1928 to 447,000 in 1937; dips a little in 1938 and 39; then falls sharply during the World War to 218,000 (1942) before rising again to 487,000 in 1945, and a peak of 1,010,000 in 1952.
Source: workersliberty.org