List of New Zealand by-elections

By-elections in New Zealand occur to fill vacant seats in the House of Representatives. The death, resignation, or expulsion of a sitting electorate MP can cause a by-election. (Note that list MPs do not have geographic districts for the purpose of provoking by-elections – if a list MP's seat becomes vacant, the next person on his or her party's list fills the position.) Historically, by-elections were often caused by general elections being declared void.

Under the Electoral Act 1993, a by-election need not take place if a general election will occur within six months of an electorate seat becoming vacant, although confirmation by a resolution supported by at least 75% of MPs is required. In 1996 the general election date was brought forward slightly, to 12 October, to avoid a by-election after the resignation of Michael Laws. Twice, in 1943 and 1969, by-elections were avoided after the deaths in election years of Paraire Karaka Paikea and Ralph Hanan by passing special acts, the By-election Postponement Act 1943 and the By-election Postponement Act 1969.

In recent years by-elections have not occurred particularly frequently – only one in the 2002–2005 parliamentary term, and none in the 1999–2002 or 2005–2008 terms. This is because most MPs who retire mid-term (e.g. Labour MPs Jim Sutton and Michael Cullen) were List MPs, so are simply replaced by the next member below them on their party list (unless that person is already an electorate MP, or does not agree). Some MPs have entered Parliament when two or more people above them on the list have declined, sometimes after pressure from their party: in 2008 Dail Jones (New Zealand First) and Russel Norman (Green); and in 2011 Louisa Wall (Labour) after five above her on the list declined.

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