Through an amendment in the Electoral Act in 1965, the number of electorates in the South Island was fixed at 25, an increase of one since the 1962 electoral redistribution. It was accepted that through the more rapid population growth in the North Island, the number of its electorates would continue to increase, and to keep proportionality, three new electorates were allowed for in the 1967 electoral redistribution for the next election. In the North Island, five electorates were newly created (including Birkenhead) and one electorate was reconstituted while three electorates were abolished. In the South Island, three electorates were newly created and one electorate was reconstituted while three electorates were abolished. The overall effect of the required changes was highly disruptive to existing electorates, with all but three electorates having their boundaries altered. These changes came into effect with the 1969 election.
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Wilson, James Oakley (1985) [First published in 1913]. New Zealand Parliamentary Record, 1840–1984 (4th ed.). Wellington: V.R. Ward, Govt. Printer. OCLC154283103.
Norton, Clifford (1988). New Zealand Parliamentary Election Results 1946–1987: Occasional Publications No 1, Department of Political Science. Wellington: Victoria University of Wellington. ISBN0-475-11200-8.