Staff at a jail which houses more than 600 sex offenders must be more alert to the risk of prisoner-on-prisoner sexual grooming, an inspection report says.
It said Rye Hill Prison, Warwickshire, had “real strengths”, but more must be done to stop inmates, especially younger ones, becoming victims.
Governor Richard Stedman said it would be “naive” to think offenders lost the ability to “manipulate” once in jail.
But he said his staff were getting better at dealing with the problem.
The Category B prison switched in 2014 from housing a mix of offenders to only those convicted of sex crimes.
The report said it was overall “performing very well” – it was safe, with bullying generally well managed, and the cells were in good condition.
It said staff “were generally aware of the particular risks associated with the sex offender population”.
“But there was no strategic approach to ensuring that all staff were aware of the potential for prisoner-on-prisoner sexual grooming and targeting, especially in relation to some of the younger prisoners held at the prison.”
Rye Hill holds some of the most dangerous sex offenders in Britain – 90% are serving sentences of 10 years or more.
Mr Stedman told BBC News: “We now have a population that is much more sophisticated and able to manipulate and condition because, let’s be honest, that’s how they’ve been able to commit a lot of their offences.”
He said many inmates had committed offences against children, adding: “It would be really naive to think those behaviours disappear when they come into custody.
“They don’t have access to children so they will often focus their behaviour on staff and their peers.
“I would recognise that we’ve had a lot of learning to do when an establishment changes in such a short period of time. It takes time to learn about those behaviours, so we’re getting ever better.”