Hackett was born in Southampton in 1901. He found employment in the British Merchant Navy transporting refugees. He became a gunner in the Royal Navy during World War I. In 1921 he moved to New Zealand and he married Ivy Lily Bradford in Dunedin in 1923; together they had four children. He became an active unionist and in 1922 Hackett gained employment at the Auckland Tramways Board. He was a prominent member of the Auckland Tramways Union for the next twenty years.
Hackett was the Member of Parliament for from 1943 to 1963, when he died. He defeated John A. Lee in the electorate after Lee was expelled from the Labour Party following the "Lee Affair". Contemporary Martyn Finlay said Hackett was an extremely effective representative for his electorate due to his ability to use the life experiences he acquired to relate personally with constituents; "Hackett learnt his trade in the best university of all - that of practical experience on the job." Hackett was described by contemporaries as a party hack, though he was well-liked by caucus members and the wider Labour Party.
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 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. On 25 July 1962 he was admitted to Auckland Hospital for an operation on his brain, which saved his life. Following the operation he recovered steadily and was discharged in early September. During his absence Nordmeyer acted as deputy leader until Hackett returned to Parliament on 27 November 1962. Following Skinner's death Walter Nash favoured Hackett to replace him when he retired prior the 1963 election, but with the death of Hackett, Nash was eventually replaced by Arnold Nordmeyer. Before he died, Hackett informed the caucus that he would also resign the deputy-leadership when Nash retired. He was replaced by Hugh Watt. He did however intend to stay in parliament and had been re-selected to contest Grey Lynn at the upcoming 1963 general election.
Death
On 19 March 1963 Hackett collapsed and died at his New Lynn home. He was buried at Purewa Cemetery. He was survived by his wife, three sons and daughter.
