Lawyers for Alan Winston Priest argued yesterday an Australian Federal Police officer created a crime when he posed as a 12-year-old Canberra boy in an internet chat room.

Priest, 59, pleaded guilty in the ACT Supreme Court to using the internet to groom a person under 16, and transmitting and possessing child pornography.

The Dunlop man was charged last year after police received a tip-off from the United States Federal Bureau of Investigation.

But Priest, who was arrested en route to what he thought would be a meeting with the boy, denied using the internet to procure a child for sex.

Priest's barrister Steven Whybrow said Australian police should not have masqueraded as 12-year-old ''Jamie'' because the FBI had already supplied evidence with which to charge Priest. The court heard Priest had sent explicit messages and child pornography to an FBI agent posing online as ''Brad'', a 14-year-old boy, in 2006.

Mr Whybrow invoked the Human Rights Act as he asked Justice Hilary Penfold to rule that the chat transcripts between Priest and ''Jamie'' were inadmissible evidence.

''We say police have created a crime, to put it in popular vernacular, they were shooting fish in a barrel,'' he said.

''It is clear that by August 2007 the AFP was aware [Priest] had committed an offence of grooming and transmitting material. The police had identified the person and there was no reason whatsoever not to arrest them and charge them with the offences committed.''

Mr Whybrow said the AFP acted improperly by inventing the child.

The hearing was adjourned to allow the Attorney-General and Human Rights Commissioner the opportunity to intervene.

Priest did not apply for bail and sought to be placed in protective custody.