The Independent Police Complaints Commission is investigating South Yorkshire Police's handling of complaints about a rock star who has admitted child sex offences.
Lostprophets singer Ian Watkins is to be sentenced next month for offences including attempted rape of a baby.
The IPCC is investigating the force's handling of a complaint made against Watkins in 2012 by his former lover Joanne Mjadzelics from Doncaster in South Yorkshire.
The 36-year-old singer, who was called a "determined and committed paedophile" in court, admitted attempted rape and sexual assault of a child under 13 but not guilty to rape - a plea the prosecution accepted.
He 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.
He will be sentenced on 18 December.
A judge has labeled a Doncaster mother's abuse of her own child with Ian Watkins as the "greatest betrayal" a mother can allow.
Ex-bandmates of paedophile Ian Watkins said they were "heartbroken, angry and disgusted" by him, and were unaware of his child abuse.