All Blacks rugby captain Mils Muliaina reckons the clamour for his teammates to sing the national anthem would die away quickly if people knew how bad they were.

Muliaina and coach Graham Henry fielded questions on Friday about the national team's unwillingness to belt out God Defend New Zealand in unison before the start of Test matches.

The issue has gained traction in the public sphere this week, with critics believing the All Blacks put too much emphasis on the haka and not enough on the anthem.

Muliaina disagrees, saying most of the team are singing, even though it may not appear that way.

"We've had a brief discussion as players and I think the majority of the group do," he said on Friday.

"If you look at the French and compare them to us, we probably just open our lips a little bit."

Muliaina believed the All Blacks players had reserved personalities, which was reflective of New Zealand as a whole, although they were all "passionate" about representing their country and about the anthem.

Muliaina nodded when asked whether some players were ill equipped to be exercising their vocal calls beyond a mumbling pitch.

"That's got to be one of the reasons (they don't sing), they're not very good singers in this team," he said.

"Jimmy Cowan doesn't sing it and I've actually just realised why, because he can't sing."

Henry chimed in by suggesting the team add a singing coach to the management team.

He was slightly more serious when asked if all players should get involved in the pre-match ritual.

"I haven't instructed them to sing the anthem yet (but) I think it's a decision they will come to," he said.

"I think they should sing the anthem, for sure."

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