The singer of what some have called the worst version of the New Zealand national anthem ever has apologised wholeheartedly before nailing the Māori version live on air.

On Saturday, American singer Crystal Collins stumbled her way through the New Zealand national anthem ahead of the Kiwis' clash against England in Denver, Colorado.

Collins appeared to miss her cue and was lost throughout the New Zealand anthem, as Kiwis players looked on perplexed.

Speaking to Radio Sport this morning Collins said she felt "horrible" about the performance.

"I would like to apologise to you and the citizens of New Zealand."

She had sung the England anthem God Save the Queen acapella, and when the New Zealand anthem came on with a backing track, she could not hear the monitor.

"I didn't have a chance to hear what the monitor would be like before the New Zealand anthem started. I could hear nothing at all."

She could sing in five languages, and had practised both the English and te reo versions "over and over again", but had done so with a different backing track.

"I was waiting for the introduction, but there was none."

The Radio Sport hosts then asked her if she would like to redeem herself.

She accepted, and belted out the version in Māori.

LISTEN ABOVE AS CRYSTAL COLLINS PERFORMS FOR RADIO SPORT

"I am so sorry it did not come out like that on Saturday," she said.

Asked what she thought of the strong New Zealand reaction to her performance, she said it was "expected".

"I felt horrible. I would have rather sang it acapella, as that was how I was rehearsing.

"I expect all the ridicule I am getting. All I am getting is warranted."

On Sunday New Zealand Rugby League CEO Greg Peters called the rendition before the game "disgraceful".

"The anthem was disgraceful, and we are very disappointed by that," he told RadioLive.

"These things happen from time to time, and it's not the first time that I've seen it happen in sport.

"The Kiwi national anthem is something we're proud of, and we will be taking steps to speak to the promoters about that in the debrief."

Peters plans to seek a "please explain" from the game's promoter, Moore Sports.

The Kiwis fell to England 36-18 in the test.