But the law change may threaten artists who do not get their work classified by Commonwealth censors. The artist Bill Henson had his contentious work judged by film censors before going to exhibition. The artist Polixeni Papapetrou, whose photograph of her six-year-old daughter on the cover of Art Monthly caused a storm last year, did not have her work sent to censors.

She criticised the law change yesterday and asked whether she could be prosecuted if her work were judged by authorities as child pornography, saying: ''I think they're barking up the wrong tree. I really think they should be going after those people who exploit children. ''I don't know of any artists who exploit children and if they do they should not be protected by any legal defence.'' The law change received cautious support from the executive director of the National Association for Visual Arts, Tamara Winikoff, who said artists were working with the director of public prosecutions on ''protective protocols so that art experts are consulted and can advise on whether the material had been produced by a genuine artist''.

''While the removal of artistic merit may seem to make artists more vulnerable to constraints on their freedom of expression, police and the ODPP need to establish the material in question is such that a reasonable person would find it offensive in all the circumstances,'' Ms Winikoff said. Asked if parents who submitted a photo of their children naked for public exhibition now needed to get those photos classified, Ms Winikoff said:''That's a matter of their own judgment.''

She said: ''It's really very rarely artists' work can be considered to be in danger of being child pornography.'' Mr Hatzistergos said: ''There will be no further artistic purpose defence. It is anomalous to describe something as child abuse material and then to have a defence of artistic purpose. Instead, the definition of child abuse material will take into account the context in which the relevant material was produced or came into existence.'' Under other changes to the law, witnesses as well as child abuse victims will be able to give evidence by video link and those they accuse will not be allowed to cross-examine them.