 Sponsored by his union, Holmes was elected unopposed as Member of Parliament for Hemsworth at a by-election in 1946 following the death of the sitting MP George Griffiths.Holmes held the seat at the next three general elections, each time with the largest Labour majority in the election.From 1947 until 1951, he was Parliamentary Private Secretary to the successive Ministers of Fuel and Power, Hugh Gaitskell and Philip Noel-Paker.