A legal challenge to stop the release of the teenage convict of the 2012 Delhi gang rape has been unsuccessful.

The petitioner, MP Subramanian Swamy, had requested the Delhi high court to stop his release, due on Sunday.

The teenager, who cannot be named as he was a minor at the time of the crime, was sentenced to three years in a reform facility in August 2013 - the maximum term possible for a juvenile.

The rape and the subsequent death of the woman had caused global outrage.

Some activists and the parents of the victim also wanted the teenager to stay in jail, saying "he can be a threat to the society".

But on Friday, the court said the convict could not be kept in the correctional home because he had served the maximum term possible under the law.

"We agree it is a serious issue. But after 20 December, the juvenile cannot be kept at a special home per law," the NDTV website quoted the judge as saying.

The mother of the victim said she was "disappointed" with the ruling and that she would consider challenging the order in the Supreme Court.

With public outrage growing over his release and threats to his life, he will be handed over to a charity for his protection and rehabilitation.

Some reports had claimed that the juvenile had been the most brutal during the crime and there were calls to try him as an adult, with many saying his punishment should be commensurate with his crime.

But during his trial, it was never proved that the teenager was any more brutal than the others, but this fact has been ignored by most people.

Case timeline

The rape and the subsequent death of the woman had caused global outrage. Photo: AFP

16 December 2012: A 23-year-old physiotherapy student is gang-raped by six men on a bus in Delhi, her male friend is beaten up and the pair are thrown out after the brutal assault

17 December: Key accused Ram Singh, the bus driver, is arrested. Over the next few days, his brother Mukesh Singh, gym instructor Vinay Sharma, fruit seller Pawan Gupta, a helper on the bus Akshay Thakur, and the 17-year-old juvenile, who cannot be named, are arrested.

29 December: The victim dies in hospital in Singapore from injuries sustained during the assault; body flown back to Delhi

30 December: Cremated in Delhi under tight police security

11 March 2013: Ram Singh dies in Tihar jail; police say he hanged himself, but defence lawyers and his family allege he was murdered

31 August: The juvenile is found guilty and sentenced to three years in a reform facility

13 September: The four adult defendants are convicted and given the death penalty by the trial court

13 March 2014: The Delhi high court confirms the death sentence

March - June: The convicts appeal in the Supreme Court and the death sentences are put on hold until the court takes a decision