After seeing active service in the Second World War, enlisting in the Royal Engineers in 1941 and later being commissioned and reaching the rank of Captain, he was elected to Parliament in the 1945 general election for the previously Conservative seat of South East Essex. He was a backbencher throughout the six-year Labour Government of Clement Attlee. The Labour Home Secretary, James Chuter Ede, presided over a redistribution of seats in the late 1940s and Gunter's Essex seat was broken up, so he switched to the seat of Doncaster in Yorkshire for the 1950 general election. Elected by a majority of only 878, his Conservative opponent, Anthony Barber, went on to unseat him by 384 votes in the 1951 general election that saw the return of a Conservative Government under Winston Churchill.
Gunter was associated with the right wing of the Labour Party and was a member of the Labour Party's National Executive Committee (NEC) from 1955 to 1966 and was president of his union, TSSA, 1956 - 64. When George Isaacs (aged 76) announced his decision not to stand for re-election in the strongly-Labour constituency of Southwark in South London, Gunter secured the nomination in time for the 1959 general election and duly returned to the Commons as a TSSA-sponsored Member of Parliament, with a majority of 12,340.
Following Labour's heavy defeat in the 1959 general election, its then leader, Hugh Gaitskell, sought to revise and moderate Labour's constitution - the so-called Clause IV dispute. The trade union leaders overwhelmingly disliked this shift and Gunter was one of the opponents. (1) Following Hugh Gaitskell's death in 1963, Harold Wilson was elected leader of the Labour Party and Gunter continued to be a Labour shadow cabinet member.
Labour narrowly won the 1964 general election and Harold Wilson made Gunter Minister of Labour. The dilemma Gunter faced was his trade unionist's natural view that trade unions should be able to negotiate responsible pay rates for their members through "free collective bargaining" but on the other hand the wildcat stikes in some parts of British industry were often seen as damaging to the economy, and "wage restraint" was the alternative.
Soon after Labour's landslide victory at the 1966 general election, the seamen's strike was where this conflict came to a head, and Gunter took the same tough line as Harold Wilson. He would later describe his stint as Minister of Labour at this time as a "bed of nails." He sought to complete his work by bringing in a new bill drawn from the findings of the Donovan Commission report on trade union power, but Wilson reshuffled him to Minister of Power in April 1968. Gunter was rumoured to have been linked with negative leaks from Cabinet and resigned from government on 1 July 1968, stating he could no longer work in a Wilson government (2). Meanwhile Gunter's successor in labour affairs, Barbara Castle, saw her proposals to reduce trade union powers in her 1969 white paper, 'In Place of Strife' fail in the teeth of concerted Trade Union opposition.
Gunter was re-elected in his Southwark constituency at the 1970 general election that saw the Labour Government replaced by a Conservative one led by Edward Heath. He was by now a senior opposition backbencher and resigned from Parliament in 1972 and was succeeded by Harry Lamborn. Gunter died in 1977. His name lives on in a block of sheltered flats for the elderly built by Southwark Council in Walworth.