NSW has refused to back the introduction of an adult-only rating for video games, despite all other states endorsing it.

Attorney-General, Greg Smith, took another direction than his national and state counterparts yesterday by abstaining from a vote on the R18+ rating.

Mr Smith, who is part of the socially conservative wing of the NSW Liberal Party, said he was concerned the rating would not prevent children accessing adult material.

Sources at the meeting of attorneys-general said Mr Smith could not understand how other states could support the classification. But outside the closed meeting Mr Smith said NSW had no intention of being the fly in the ointment. ''I'm sure that there will be a reasonable compromise established.''

The chief executive of the Interactive Games and Entertainment Association, Ron Curry, said the in-principle agreement was a big step towards ''a robust ratings system that best equips parents to manage their children's access to appropriate content'' while allowing adults to play games of their choice legally.