High Commissioner to the UK Phil Goff caused offence to the Māori King at an event for the New Zealand delegation in London.
Goff forgot to perform a karakia to open the event at the High Commission, and then went on to say that no one in the room had experienced a coronation before - right in front of Kīngi Tuheitia.
A spokesperson for Kīngi Tūheitia, Ngira Simmonds, got up and explained that after Saturday, many people in the room will have in fact been to three coronations.
"The complete disregard of the … coronation of Kīngi Tūheitia Potatau Te Wherewhero VII and of course his mother, the late Māori Queen. This will be Kīngi Tūheitia's third coronation.
"The question was asked, 'Who has been to a coronation before?' Well, the king will now, after Saturday, have been to three."
Simmonds said the lack of recognition for the Kīngitanga movement is a struggle Māori have felt for some time, but they are committed to working with the government to improve that.
"I don't think Māori can stay silent when we experience things like we did this afternoon."
Goff spoke after Simmonds, and apologised for not following protocol. He declined to make further comment.
Kīngi Tūheitia was elected in 2006. While the role is not technically hereditary, every monarch so far has been a descendant of the first, Pōtatau Te Wherowhero.
Prime Minister Chris Hipkins, speaking to Morning Report after the faux pas, said it was "certainly regrettable".
"It was a mistake. I think it is important, you know, in these sorts of events that we do acknowledge the Crown-Māori relationship, and Kīngi Tūheitia clearly has a relationship with the Crown over here - we should acknowledge that.
"The fact that he's here, I think, is a recognition of that, you know - here as part of the New Zealand delegation. I think it's important that we acknowledge and celebrate that."
He said Goff, who used to lead the Labour Party and for a time was the mayor of Auckland, did not intend to "take away from the significance of Kīngi Tūheitia's coronation, or any of his predecessors for that matter".
"Clearly there's a reminder here that we can think more carefully about how we do that in the future."
Hipkins was asked if he would be asking King Charles if an apology for colonisation was in the works. Te Pāti Māori - which earlier this week made headlines after poaching a senior Labour MP - has called on the monarch to acknowledge the "horrific impacts" of colonisation, including genocide and slavery.
"We have a process in New Zealand that you know, through the Treaty settlements process where apologies are issued by the Crown for, you know, past injustices and past wrongs," Hipkins replied.
"But you do need to have a process to identify you know, what those injustices were and what the apology is for. And we do have a process for that, and it has happened and it will continue to happen. We've still got a way to go, but I think we've made progress on that, so that that's New Zealand's process."
He said it was not his role to "be proffering advice to other countries around how they should approach their relationships with their indigenous populations".
"I can certainly speak to New Zealand experience as I do, and I do get asked about that around the world when I when I'm visiting as a New Zealand government representative. I'm certainly happy to share New Zealand's experience, but I think ultimately those countries need to figure out how best to approach that with their context in mind."