Image copyright NZ Government

Voting began on Friday in New Zealand's referendum on a potential replacement for their national flag.

New Zealanders have just under a month to send in a postal ballot on which of five potential new flags they prefer.

A second vote in 2016 will ask whether they want to replace the existing flag, which features the UK's Union Jack, with the new design.

Prime Minister John Key has said the current flag is not representative of modern New Zealand.

He also believes it is too similar to Australia's, but has admitted that polling indicates most New Zealanders would rather keep it.

Media playback is unsupported on your device Media caption What do schoolchildren think of the new flag designs?

The Flag Consideration Panel received 10,292 entrants to its nationwide design competition.

Not all were entirely serious, though some of the rejected designs - including Laser Kiwi - gained something of a cult following.

Media playback is unsupported on your device Media caption New Zealand long-listed 40 designs - but not any of these

The official longlist reduced the number of potential flags to 40.

Four designs were then on the shortlist announced in September, but there was criticism that they were too similar or uncreative.

Three featured a fern design and the fourth the curving koru Maori symbol.

After a social media lobbying campaign, the government passed a bill through parliament so that a fifth design - called Red Peak - could also make the final cut.

To help people make a decision, the five flags are being put on display across the country.

Sets of flags are being given out free to communities who have five suitable flagpoles to display them from, so the public can see them in "real-life situations".