The by-election was caused by the death of incumbent MP Angus McLagan of the Labour Party on4 September 1956. McLagan, who had represented the electorate since 1946, was hospitalised in early August 1956 suffering from a chest ailment before dying several weeks later.
Candidates
;Labour The Labour Party selected Mick Connelly as its candidate. He was the son of MLC Michael Connelly and had contested in 1954. Initially Mayor of Kaiapoi Norman Kirk, who had stood for Labour in two years earlier, sought the Labour nomination, but eventually withdrew from the selection contest. Rotorua MP Ray Boord spoke at public meetings in Connelly's support. ;National Balfour Grieve Dingwall was chosen as the National Party's candidate. He had contested the electorate previously at the 1954 general election. Bill Sullivan, the Minister of Labour, made several speeches in Dingwall's support. ;Social Credit Founder of the Social Credit PartyWilfrid Owen contested the by-election. In the previous election he had contested the nearby seat of. His campaign focused on the plea that Social Credit needed a voice in parliament and targeted Labour voters to support him in the by-election given the result could not change the government. Former Labour MP, turned Social Credit activistFrank Langstone spoke at hustings in support of Owen. ;Others Ernest Yealands representing a splinter group of the Social Credit Party contested the seat against Owen, where he was expected to draw away "a few hundred votes from his one-time leader". Additionally Richard Israel Charles Grenfell had initially chosen to contest the seat as an independent, but withdrew. However, his decision to withdraw came after the ballot papers were printed.
Campaign
A prominent issue in the by-election was the question of state-aid to private schools. Connelly and Dingwall opposed the notion, Yealands supported it while Owen sidestepped the issue stating that under Social Credit state-aid would not be necessary. There was also a hotly argued debate between the supporters of Connelly and Owen over whether Labour's first Prime MinisterMichael Joseph Savage was a social crediter. The debate spilled over into newspapers, filling correspondence columns and letters to editors for over a week.
Results
The following table gives the election results: Connolly was re-elected at the subsequent general election confirming him as the MP. He would represent it until 1969 when he transferred to the neighbouring electorate.
