The former lead singer with the multi-million selling rock band offered a last-minute change of plea ahead of a planned trial.
Former Lostprophets frontman Ian Watkins has admitted a string of sex offences, including two charges of attempting to rape a baby.
The singer had faced 24 sex-offence charges but pleaded guilty to 11 of them at the last minute, nine of which were unchanged and two of attempted rape of an infant, which were downgraded from actual rape.
The charges included sexually touching a one-year-old and encouraging a mother to abuse her own child during a webcam chat. Watkins also admitted possessing and making child abuse images as well as being behind the plot to rape the child.
Watkins, 36, from Pontypridd, south Wales, insisted he had no memory of what would have been key video evidence at the trial showing him abusing his victim, the court heard.
Prosecuting QC Chris Clee said camcorder footage shot in a London hotel room showed Watkins perform a sex act on the child. Computer analysts found the footage had been uploaded to an online storage facility.
Mr Clee said that following this meeting, Watkins and his co-accused - a woman who cannot be named for legal reasons - exchanged emails about how they would not go "easy" on the child next time.
The court also heard details of a plot to turn babies in subservient sex slaves using hard drugs.
Watkins and the woman swapped messages where they discussed plans to blow crystal-meth smoke into the child's face at a secret meet up in a Cardiff hotel.
On March 23, Watkins sent the woman a message saying he wanted a "summer of filthy child porn" and how he wanted to take things "to the next level" and spoke of a desire to "cross the line".
The disgraced rocker was originally charged with actual rape but insisted sex with the child did not take place. Mr Clee told the judge that both attempted rape admissions were accepted and acknowledged there was an argument regarding what the video evidence seized from Watkins's laptop actually showed.
"From the footage, there is an argument as to whether the full offence is made out," he told judge Mr Justice Royce.
"If it is made out, it is minimal. There is so little difference between the full attempt and the attempt as to make no difference. We are prepared to accept the pleas as tendered."
Mr Clee also told the judge that the prosecution had in mind the effect on the jury of watching the explicit video footage.
Catrin Evans, head of the complex casework unit at 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."
Detective Chief Inspector Peter Doyle described the case as "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," he said.
He added: "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.
"A significant amount of electronic data has been retrieved from computers and web-based storage which has provided crucial evidence to support the case.
"Today's outcome does not mark the end of our investigations and we will work tirelessly to identify any other victims or witnesses and seek the justice they deserve."
As talk of sentence was discussed in court, a pale faced and grey-haired Watkins began shaking in the dock. He will be sentenced on December 18.