Following Labour's defeat in 1960, Hackett served on the opposition frontbench and in June 1962 Hackett was elected as the deputy leader of the Labour Party, in preference to Arnold Nordmeyer and Hugh Watt, upon the unexpected death of Jerry Skinner. He beat Nordmeyer on the second ballot after Watt (a fellow Aucklander) had been eliminated in the first ballot for the position, as a compromise candidate as was regarded by many within the Party as a middle roader. Hackett also likely received sympathy votes as he was known to have been ill.