A group pushing for a new Australian flag is encouraging New Zealanders to ditch the Union Jack and vote for the alternative option in the flag referendum.
Ausflag, an organisation founded in 1981 to campaign for a new Australian flag, is using an advertisement in the Herald to reach out to Kiwis and implore them to choose Kyle Lockwood's silver fern design.
The advertisement says New Zealand beats Australia "at most things (except cricket)".
"It seems we'll be the last nation in the world to have a flag which symbolises a British branch office and resembles Britain at night.
"In the spirit of our historic and continuing friendly rivalry, we wish you the best of luck."
Ausflag executive director Harold Scruby said the advertisement is "all about the spirit of challenging each other".
He has also sent a letter to Prime Minister John Key, where Mr Scruby explains that if New Zealand changes its flag, "many Australians will be calling on our political leaders to follow your lead".
"You now have a fabulous opportunity to make history. In 100 years, perhaps even 50, few are likely to know or remember whether you reduced inflation, increased employment or balanced the books.
"But ... every New Zealander will know that you gave New Zealand its own flag."
Voting for the flag referendum begins tomorrow and runs until March 24.