Born in Manchester, Douthwaite left school at the age of eleven, working first for a tea merchant, then for the Bradford Dyers Association.
He was elected to the ILP's National Administrative Committee (NAC) in 1910, defeating W. Williams to represent Cheshire and North Wales, then later in the year contributed along with J. M. McLachlan, Leonard Hall and J. H. Belcher to the Green Manifesto.
However, that year he was elected to Bredbury and Romiley Urban District Council (UDC), winning on the drawing of lots, as he had tied with a Conservative candidate.
He was immediately elected to its Standing Order Committee, alongside Duncan Carmichael, Peter Petroff and E. C. Fairchild, and the four worked together to ensure voices in the party opposing British rearmament were heard.
[1] Douthwaite focused on local politics during and after World War I, chairing the UDC and the Macclesfield Divisional Labour Party.