Hemmerde was first elected a Liberal MP at a by-election for East Denbighshire in 1906. He held the seat in January 1910 but fought and lost Portsmouth in December 1910. In 1912 he returned to parliament for North West Norfolk. Hemmerde strongly supported the taxation of land values and land was a key issue in his campaign. He subsequently joined Lloyd George’s land enquiry. He was out of parliament after 1918 and in the early 1920s joined the Labour Party. He had a final stint in parliament as Labour MP for Crewe 1922-24. Outside parliament Hemmerde was Recorder of Liverpool from 1909 until his death and was a moderately successful playwright.