[1][2] Irwin was selected by the Boilermakers as a prospective Parliamentary candidate, and at the 1929 United Kingdom general election, he stood in Montrose Burghs.
As a result of this, he was selected to stand in the 1930 East Renfrewshire by-election by the local Labour Party and Trades Council.
After lengthy deliberation, it refused to approve his candidacy, making Irwin the first independent ILP candidate in many years.
[2][3][4][5] Irwin's candidacy marked a new stage in the split of the ILP from the Labour Party, which was finalised in 1932.
However, Irwin chose to remain with the Labour Party, standing for it in Greenock at both the 1931 and 1935 United Kingdom general elections.