A man who is already serving a 23-year prison sentence for leading a gang that sexually exploited children in Rotherham has admitted raping a 13-year-old girl.

Mohammed Imran Ali Akhtar was charged as part of Operation Stovewood, the huge series of National Crime Agency (NCA) investigations which began after child sexual exploitation on a massive scale was identified in the South Yorkshire town, provoking a national outcry.

The 42-year-old appeared at Sheffield Crown Court on Tuesday, where he pleaded guilty to two counts of rape and two counts of indecent assault, which he committed between August 2001 and July 2002, the Crown Prosecution Service (CPS) confirmed.

He was jailed for 23 years at the same court in 2018 by a judge who said he was the ringleader of a gang who “perpetrated, facilitated and encouraged” abuse of five victims who were “vulnerable in the extreme”.

The CPS said the latest conviction relates to a girl groomed by Akhtar, who provided her with alcohol and drugs each time they met.

A spokeswoman said the defendant would threaten to drive her to unknown locations and leave her stranded if she did not comply with his demands for sex.

On one occasion, when she did refuse to engage in sexual activity, she recalled having to walk for hours after she was kicked out of the car by Akhtar in the early hours of the morning, the spokeswoman said.

Akhtar will be sentenced on December 18.

When he was convicted along with five others in 2018, one of the complainants told a trial that she had had sex with “at least 100 Asian men” by the time she was 16, and another said she was gang-raped in a forest and threatened with being abandoned there.

Zoe Becker, legal manager for the CPS, said: “Mohammed Imran Ali Akhtar targeted the young victim and used drugs and alcohol to groom her for sex.

“The lifelong physical and emotional trauma caused to victims by men like Akhtar cannot be understated.

“We would like to thank the victim in this case for coming forward and reporting this devastating crime.

“I hope this conviction sends a clear message that the CPS, working alongside the NCA, will continue to relentlessly pursue justice and prosecute those who sexually exploit children, whenever that abuse took place.”

Operation Stovewood senior investigating officer Philip Marshall said: “I would like to pay tribute to the victim in this case, who had the bravery to come forward and tell her story, which was key to this conviction.

“While supporting victims like her remain our priority, we remain determined to do all we can to identify and bring offenders to justice, and to continue to work in partnership with all services in South Yorkshire.”

Operation Stovewood, which is investigating allegations of abuse in Rotherham between 1997 and 2013, is the largest law enforcement investigation into non-familial child sexual abuse in the UK.

The NCA said more than 200 people have been arrested so far and 24 convictions secured.