Jenkins became active in local politics, representing the Labour Party on
Monmouthshire County Council. He was also a strongly militant socialist, agitating for rapid and violent change. During the
General Strike of 1926 he was arrested on disputed charges, hauled before the magistrate and sent to prison for nine months, although this did not prevent him from returning to the
National Executive Committee of the Labour Party. Throughout the 1920s and 1930s Jenkins continued to promote the sectional interests of miners and the Labour movement. He was the agent for the Eastern Valleys District of the
South Wales Miners' Federation from 1921 to 1933 before serving as vice-president of the Federation. At the
1935 general election he was chosen as the Labour Party candidate for
Pontypool, one of the party's safest seats, to replace
Thomas Griffiths. With the rise of totalitarian dictatorships during 1930s his interests spread from coal and unemployed miners to poverty more generally and education, as well as foreign affairs. In 1937 his views on rearmament and the threat of global conflict attracted the attention of the Labour leader,
Clement Attlee, for whom he worked as
Parliamentary Private Secretary. In March 1945, during the
wartime coalition, he was briefly appointed Parliamentary Secretary to the
Ministry of Town and Country Planning. In the
Attlee ministry, he became Parliamentary Secretary to the
Ministry of Education. Suffering from illness, he was forced to retire from the Government in October 1945, so losing the opportunity to attain a
Cabinet position. He died at
St Thomas' Hospital in London on 25 April 1946. ==Arthur Jenkins Indemnity Act 1941==