Wellington - It wasn't the scoreline that angered New Zealanders after their rugby league Test loss to England, but what was dubbed the "worst" rendition of their national anthem.

New Zealand Rugby League chief executive Greg Peters described singer Crystal Collins' version of "God Defend New Zealand" as "disgraceful" and urged promoters to explain.

Saturday's match was played in Denver to promote rugby's 13-man version in the United States, but the talking point became the way Collins stumbled through the anthem without appearing to know the words or tune.

Television commentator Glen Larmer called it "the worst rendition" he had ever heard.

Peters told RadioLive on Monday "the anthem was disgraceful, and we are very disappointed by that".

"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," he added.

New Zealand blew an early lead to lose the game 36-18, but when fans took to Twitter they only wanted to vent their frustration at the butchering of the national song.

"The anthem was a bloody disgrace. An embarrassment," tweeted Jason, while KY Possum said: "Hubby woke up during Kiwi anthem & complained about what he thought was a bloody cat fight outside." 

Former Samoa international Henry Faafili asked: "Can the lady who did the National anthem please learn it first?"