In Australian English, the word ‘labour’ is not spelled ‘labor’. The misspelling originated from the proceedings of the Federal Conference in 1902. In 1905 and 1908, they used the spelling ‘Labour’. In 1908, a motion to use the title ‘Australian Labour Party’ was carried by 22 votes to 2. Despite this, they again used the misspelling of ‘Labor’ after 1912. The miscarriage has continued ever since. This is typical.
“[Ross] McMullin observed that the spelling ‘Labor Party’ had more to do with the chap who ended up being in charge of printing the federal conference report than any other reason”. This is also typical.
And then despite the adoption of ‘Labor’ at a Federal level, it took decades for the official spelling to achieve widespread acceptance.
Source: McMullin, Ross (1991). The Light on the Hill: The Australian Labor Party 1891–1991.
Source: Wikipedia