(CNN) New Zealand's acting Prime Minister Winston Peters has accused Australia of copying his country's flag, telling its neighbor to get its own design.

"We had a flag that we've had for a long time, copied by Australia," Peters told local network TVNZ on Tuesday.

"They (Australia) should actually change their flag and honor the fact that we got there first with this design," added Peters, who is filling in for Prime Minister Jacinda Ardern while she is on maternity leave.

The flags are indeed similar. Both are based on the British ensign, with a dark blue background, a United Kingdom Union Flag in the top left corner and the Southern Cross star constellation.

Among the few distinguishing features is that Australia's stars are white, rather than red and the flag also features an extra star with seven points representing the Australian states and territories.

New Zealand's flag was adopted in 1902, five decades before Australia's current flag was officially recognized in 1954. Though various versions of the Australian flag have been used since 1901.

Delicate time in NZ-Australian relations

Peters' comments come at a delicate time in trans-Tasman relations, after the detention of a 17-year-old New Zealander in an adult detention facility in Melbourne, Australia, earlier this month that sparked outrage in New Zealand's capital, Wellington.

Australia has deported hundreds of New Zealanders in recent years, but the incident involving the 17-year-old boy marked a low point in relations between firm allies, according to some analysts.

Read more: Design secrets of world's flags

It's not the first time New Zealand has wrested with its flag design -- in 2016 the country held a referendum over whether to ditch the Union Jack and switch to a silver fern design.

New Zealand voted to stick with the current version -- but only after spending $17.6 million on the referendum.