The Australian Rugby Union (ARU) has leapt to the defence of referee Stuart Dickinson after his performance in New Zealand's 20-6 win over Italy was slammed by IRB referees' boss Paddy O'Brien.

New Zealander O'Brien criticised the Australian's handling of the scrum during the All Blacks' dour victory over the Italians at the San Siro Stadium in Milan on Sunday.

He then later visited Graham Henry's side after the game and apologised on behalf of the IRB for Dickinson's performance.

In a statement released on Friday, the ARU expressed surprise at O'Brien's comments and said the IRB practice is to avoid singling out referees and making public comment about their performances.

"Following the negative and very public review of Stuart Dickinson, we expect to see this transparent approach adopted on a consistent basis for all elite referees in the future," the statement said.

"The ARU thinks that the criticism of Dickinson, the leading referee in Australia for a number of years, was lacking in balance.

"The analysis of scrums is an inexact science and the ARU is happy to discuss the findings of its own analysis with Mr O'Brien."

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