The Chief Censor says there are no rules of classification for live or theatre productions.
A special Christmas performance at Downstage Theatre in Wellington drew gasps on Friday night from its audience of foster children and their carers it contained sexually suggestive material and swearing.
Some 132 children in the care of Child, Youth and Family aged between six and 17 were watching An Adagio Christmas when one character called another by an obscenity and told them a situation was "B-S".
Another character playing a romance novelist wrote about losing one's virginity and then mimed a slap-stick style orgasm.
Chief Censor Bill Hastings says the Classification Act does not apply to live performances and theatres are not required to tell audiences a production may contain offensive material.
Mr Hastings says producers should inform people as much as they can about the contents of their productions and parents should do their research before taking children to the theatre.