One of Queensland's most notorious rapists, Robert John Fardon, will be a free man in October after the State Government lost a court bid to keep him under supervision.

Key points: Fardon raped victims over 20-year period

Fardon raped victims over 20-year period Court rules he will no longer be monitored having served sentence

Court rules he will no longer be monitored having served sentence Victim devastated about Fardon's impending release

Fardon — a serial predator who once raped a 12-year-old girl at gunpoint — will no longer be subject to curfews, counselling sessions and restrictions on where he can live.

The 69-year-old has a history of sexual offending dating back to the 1960s, and in 1989 he was jailed for raping and assaulting a woman.

He was due to be released in 2003, but law changes allowed authorities to keep him behind bars until he was granted supervised release in 2007.

The following year he was charged with rape and found guilty, but the conviction was later overturned on appeal.

Since 2013, Fardon's exact living address has been kept secret, but according to court documents, he has been forced to stay with other sex offenders near a jail precinct.

Sharon Tomlinson was the 12-year-old who fell victim to Fardon in 1978, and over the years she has spoken out about her fears if he was to be released.

"He stole my innocence. He took a part of me I can never ever get back," she told ABC Radio Sunshine Coast on Tuesday.

"I believe he is a high risk to the community still, and will be until the day he dies.

"I don't know where he is and I'll never know where he is. There could be a likelihood that I could run into him on the street. That's quite frightening for anyone that's gone through something like that."

Sharon Tomlinson said she was disappointed her attacker will be released. ( AAP file photo: Dan Peled )

No 'reasonable grounds' for extending order: judge

Lawyers for Attorney-General Yvette D'Ath had sought to extend the supervision order when it expires in October, but their application was rejected by the Supreme Court on Monday.

According to the court judgment, the Attorney-General's lawyers argued it would be "horrendous" if Fardon re-offended.

They argued one of the reasons he had not re-offended in recent years because he lived close to the jail.

They also said the risks of him re-offending would be heightened because he would no longer be compelled to attend sessions with a psychiatrist, and had not organised a place to stay once the supervision order expired.

However Justice David Jackson ruled "there [were] not reasonable grounds" for extending the supervision order.

Justice Jackson said he had taken into account psychiatrists' evidence, which stated there was a "low risk" of Fardon re-offending.

"He has to a large degree cooperated with case officers and there is no evidence of an ongoing proclivity to criminal offending," Justice Jackson said.

"There is no evidence that a sexual paraphilia now exists. There is no evidence of ongoing sexual preoccupation."

The court heard Fardon, who suffers from emphysema, attended more than 180 sessions with a psychiatrist between August 2014 and February 2018.

A spokeswoman for Ms D'Ath said the Attorney-General had not decided whether to appeal the ruling.

"The Attorney-General is examining the judgment and will consider her position," she said.

Shadow Attorney-General David Janetzki called on the Government to seek urgent legal advice to appeal.

"The safety of our community is paramount and we need to ensure vulnerable children are protected," he said.

Child safety advocate Hetty Johnston said she was frightened for the community, if the Government did not step in and stop Fardon's release.

"If ever there was a candidate for being permanently jailed, it's him," she said.

"He's been in and out of jail his whole life, and for his whole life he's been, not just sexually assaulting and raping girls, but violently with guns.

"This man will offend again, I put my house on it, he will do it again and god help that next child."