New Zealand Prime Minister Chris Luxon has denigrated the intelligence of Australians in a joke during question time in parliament.

“In my dealings with Australians it always pays to be incredibly simple,” he said on Wednesday.

The quip recalled former Kiwi leader Robert Muldoon’s infamous line that New Zealanders leaving for Australia “raised the IQ of both countries”.

However, Luxon’s comment fell flat in parliament, with Foreign Affairs Minister Winston Peters showing indifference and other MPs gasping or sounding notes of outrage.

The gaffe came in response to questioning from Labour opposition leader Chris Hipkins over the government’s use of the Maori language, known as te reo Maori.

This week, broadcaster TVNZ revealed Culture Minister Paul Goldsmith had told officials to remove te reo expressions from an invitation to Matariki, the annual celebrations of the Maori New Year.

The invitation was bound for Tony Burke, Australia’s Multicultural Affairs minister.

The Maori words included the greeting “tena koe” (meaning hello), the sign-off “naku noa, na” (which became ‘yours sincerely’), and the removal of the widely-accepted Maori name for New Zealand: Aotearoa.

Te reo is an official language of New Zealand, along with sign language and English, and increasingly spoken by Maori after decades of decline – in part due to hostile government policies.

Luxon’s right-leaning coalition – of the conservative National, free-market libertarians ACT and populist NZ First parties – has reduced its use in government since taking office last November.

The government has issued edicts to public servants to stop communicating in te reo, and asked government departments to rebadge with English names, scrapping or de-prioritising Maori names given more prominence during Jacinda Ardern’s government.

Goldmsith’s instruction to remove the Maori greetings – which are commonplace in New Zealand – drew criticism from Labour, particularly given it was correspondence relating to Matariki, New Zealand’s sole indigenous public holiday.

“It’s just a shameful act … it’s an insult, not just to Maori people but to this country,” opposition Maori development spokesman Willie Jackson told TVNZ.

“Here we are trying to celebrate this language and you’ve got a minister acting contrary to that.”

Goldsmith said he didn’t think Burke would know what Aotearoa meant.

“It’s hardly the scandal of the century. I just didn’t think it needed a lot of te reo in it … I thought, let’s just keep it simple,” he said.

In parliament on Wednesday, Hipkins included Goldsmith’s letter in a line of questioning to Luxon around ministerial standards.

“We value te reo in this government,” Luxon said.

“The correspondence was being directed to an Australian minister overseas and, what I’d say to you – in my dealings with Australians, it always pays to be incredibly simple and clear and use English.”

Luxon is no stranger to Australia, living in Sydney for five years during his pre-politics corporate career with Unilever.

His son Will is an Australian citizen, and his daughter Olivia graduated from the University of Melbourne last year.

“I love Australia,” he said in a 2022 interview.

“If I couldn’t be a Kiwi I’d be an Aussie. Absolutely. I just love the confidence and optimism of the joint.”

It is not Luxon’s first Maori language-related misstep.

In December, he told public servants who wanted to learn te reo they should pay for it themselves. It was later revealed he had charged taxpayers more than $3000 for his own tuition.

-AAP