The by-election was called following the invalidation of the preceding 1922 general election result due to irregularities.

[1] When the preliminary counts for the 1922 general election in the Oamaru electorate were announced, Ernest Lee was ahead of John Andrew MacPherson by just one vote.

A recount was ordered, during which some irregularities came to light, and Lee asked for a judicial review.

The court case was heard at the Supreme Court in Wellington by Sir Robert Stout and Justice Alexander Samuel Adams, who declared the election void and ordered the parties to pay their own expenses.

At the subsequent general election in 1925, Lee in turn defeated MacPherson.