[1][2] William Tanner represented the Christchurch seats of Heathcote from 1890 to 1893 and then Avon from 1893 to 1908, when he was defeated.

[3] Among the radical policies that Tanner approved of were-the nationalisation of land, periodic revaluation of Crown leaseholds, and the establishment of a state bank.

[4] He was a member of the Woolston Municipal Council (1893–1900), Canterbury Hospital Board (1911–14), and Secretary to the Bootmakers' Union of Christchurch.

Tanner was considered to be "the first Labour candidate" to be elected to the New Zealand House of Representatives in 1890 when he was successful in the Heathcote electorate.

The Christchurch Press said of him: "Nice voice, speaks slowly with a precision almost painful...Hard-working, intelligent, industrious and no reason to doubt his honesty".