An Australian radio show that hooked up a teenage girl to a lie detector and forced her to admit she was raped returned to the airwaves on Tuesday, with its hosts apologising over the stunt.

The 'Kyle and Jackie O Show' was yanked off air earlier this month after sparking outrage when the 14-year-old's mother prompted her to reveal during a live broadcast that she had been raped when she was 12.

Prime Minister Kevin Rudd led a barrage of criticism from psychologists, broadcasters, child protection and rape crisis groups over the girl's treatment.

Broadcaster 2Day FM said it decided to allow hosts Kyle Sandilands and Jackie O back on the air after introducing safeguards during live broadcasts, including a seven-second delay.

"It's pretty much obvious to everyone that the whole thing was a disaster from start to finish, a complete disaster," Sandilands told listeners.

The "shock jock", infamous for stunts such as drinking breast milk and launching a competition to find Sydney's smallest penis, lost his job as a judge on television's 'Australian Idol' over the incident.

He said the radio station had no idea the girl would make the rape disclosure before she went on air and claimed he was trying to help her mother address concerns about her daughter.

"The whole reason that the mum came on here in the first place was because she was a single mum that was worried sick about her daughter, and she had nowhere else to turn and she didn't know what she was going to do," he said.

NSW Premier Nathan Rees said the radio hosts should not have been allowed to return.

"They well and truly overstepped the mark a few weeks ago," he told reporters.

Police dropped an investigation into the girl's rape claims after she told them she did not want the matter pursued.

Australia's media regulator has launched an investigation into whether the lie detector segment breached broadcasting guidelines.

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