Ian Watkins, singer of Welsh rock band Lostprophets, has pleaded guilty to a series of "depraved" child sex offences including attempted rape of a baby.
He had previously "furiously denied" the allegations.
The 36-year-old from Pontypridd and two women had been due to stand trial at Cardiff Crown Court.
Watkins pleaded guilty to attempted rape and sexual assault of a child under 13 but not guilty to rape. This was accepted by the prosecution.
Sentencing will take place on 18 December.
Prosecuting barrister Chris Clee QC told the court: "Ian Watkins was the lead singer in a successful band called the Lostprophets.
"He accepts he was a determined and committed paedophile."
Watkins also admitted three counts of sexual assault involving children and six involving taking, making or possessing indecent images of children and one of possessing an extreme pornographic image involving a sex act on an animal.
The evidence against the defendant came from computers, laptops and mobile phones.
The court heard that he filmed and kept the episodes of abuse - which took place in various hotels in London and south Wales - which were recovered by police.
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Who are Lostprophets?
Lostprophets, an alternative rock band from Pontypridd in the south Wales valleys, formed in 1997.
The band was founded by lead singer Ian Watkins, bassist Mike Lewis, drummer Mike Chiplin and guitarist Lee Gaze.
They released five albums, and their biggest hits included Last Train Home and Rooftops. The band sold about 3.5 million albums worldwide.
Their music received heavy airplay on mainstream radio stations and they were a staple festival act at the likes of Reading and Leeds, but they struggled to be taken seriously in the rock fraternity as their music became increasingly pop-orientated.
The band announced they were splitting up in October, ten months after Watkins was charged.
Former south Wales music journalist Gavin Allen says: "They achieved real success, but their career - and back catalogue - will now be so tainted that it is hard to see any radio stations playing their music again.
"Their legacy has just vanished."
Some of the evidence was too extreme and distressing to report.
'Teach babies to take drugs'
Referring to two women standing alongside Watkins in the dock, Mr Clee said: "Both women sexually abused their own children and made them available to Watkins for him to abuse."
The court was told how the abuse of the children by all parties was also evident in text messages.
Watkins sent a text to one of the women saying: "If you belong to me, so does your baby."
In an exchange involving the other woman, she sent Watkins a message along with an image of her child to the effect that her child needed to know she was not loved.
Watkins also planned to "teach" the babies how to take drugs, the hearing was told.
Mr Clee said drugs played "a significant part in his offending against children".
Police found meth, cocaine and GHB during their searches.
Mr Clee told the court drugs were a "regular theme" in his dealings with the two other defendants.
Claiming his innocence, Watkins had told police during interviews he was being stalked by "a crazed fan" and other people had access to his computers.
He claimed he was the "victim of a malicious campaign".
Ian Watkins Watkins used his fame to attract young girls
The court heard in Oct 2006, Watkins met up in a hotel with a 16-year-old girl from Boston, who he had met during during a Lostprophets concert.
She dressed in a schoolgirl's outfit and he filmed their encounter.
In Oct 2008 he filmed himself having sex with another 16-year-old girl, who was also a Lostprophets fan.
Exploited status
One of the two women charged alongside Watkins, Woman A, admitted the attempted rape of a baby after denying rape and two charges of sexual assault as well as taking and distributing an indecent photograph of a child.
Woman B pleaded guilty to conspiring to rape a child, three sexual assault charges and four charges of taking, possessing or distributing indecent images.
After hearing legal argument from barristers, Mr Justice Royce called the jury into court and told them: "There will not be a trial in this case. The defendants have all pleaded guilty to nearly all the charges against them. The prosecution does not seek a trial in these circumstances.
"You have been saved from having to watch extremely graphic and distressing material."
Sally O'Neill, defending Watkins, said the singer was under the care of a psychiatrist.
Speaking outside the court, Det Ch Insp Peter Doyle from South Wales Police said: "This investigation has uncovered the most shocking and harrowing child abuse evidence I have ever seen.
"There is no doubt in my mind that Ian Watkins exploited his celebrity status in order to abuse young children.
"Today's outcome ensures the three people responsible have been brought to justice."
"Two very young children have been removed from this abuse and given a future that would otherwise have been denied them.
"The investigation has been extremely complex and challenging with key information and evidence being identified from witnesses worldwide."
He added that today's guilty pleas did not mark the end of the investigation and the force would work "tirelessly" to identify other victims or witnesses.
Catrin Evans, head of the Complex Casework Unit for the Crown Prosecution Service, Wales, said: "The three defendants in this case have admitted very serious sexual offences committed against extremely young children, demonstrating sexual exploitation at its worst.
"A number of the victims are too young to be able to understand what has happened to them, yet the defendants exploited them for their own gratification."
www.bbc.co.uk/news/uk-wales-25108439
