The daughter of Boomtown Rats star Bob Geldof posted the names of two women involved in the case on Twitter after reportedly reading them on a US-based website - but has since removed them.
Peaches Geldof named the two women who allowed their babies to be abused by Ian Watkins
In two tweets made on Thursday afternoon, the AG wrote:
"We understand that the names of the co-defendants in the Ian Watkins case have been posted online."
A second tweet added: "Victims of sex offences have lifetime anonymity. Publication of info which could identify them is a criminal offence & a police matter."
It comes two days after the former Lostprophets frontman pleaded pleaded guilty to a series of "depraved" child sex offences including admitting to two charges of attempting to rape a baby.
Two women, the mothers of babies targeted by Watkins, have not been named to protect the identity of their children. Both women also face jail.
Other defenceless young victims of Watkins's sexual abuse are also protected by automatic anonymity.
Ian Watkins will be sentenced on 18 December
The horrific case has triggered a flurry of activity on Facebook and Twitter, prompting South Wales Police to also issue a warning about identifying the victims involved in the case.
Detective Chief Inspector Peter Doyle added: "Clearly there is strong public feeling about this case and many people are using social media outlets to talk about the issues involved.
"However, there is a very real danger that some of the detail being posted will lead to the identification of victims which will cause a great deal of distress to them and their families."
Watkins will be sentenced on 18 December.
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