CNN  — 

New Zealanders have begun voting whether to replace their flag with a new contender chosen late last year.

The Silver Fern (black, white and blue) was selected by popular vote to go up against the existing standard, beating out four other contenders in a nationwide referendum.

Now Kiwis will pick whether to ditch the current flag – which features a British ensign – that has flown over the country for more than 100 years.

The postal referendum closes on March 24, after which the flag with the most votes “will be the official flag of New Zealand,” according to the country’s election authority.

Critics say the current standard is anachronistic and too similar to the Australian flag.

Prime Minister John Key, who has been the driving force behind changing the flag, said that the silver fern is a historical symbol of the country.

“That’s the national symbol of New Zealand –that’s what we’re known by,” he said during an interview on the Newstalk ZB radio show.

“The reason why I support the change of a flag is simply because we will wear it, use it and promote it more. It’s therefore all about national pride and recognition of our country and showing the world how great we think New Zealand is.

This may become New Zealand's official flag.

And I don’t think we do that very much with our current flag.”

However, in the latest One News Colmar Brunton poll, two thirds (63%) of Kiwis said they favored keeping the current flag.

Only 26% of respondents wanted to adopt the Silver Fern standard.