David Cameron has described the Oxfordshire paedophile ring case as "absolutely appalling" and "shocking".
The Prime Minister, whose constituency is in the county, said police, social services and the council would have to answer "searching questions".
"There's no doubt that first of all it's good that those who did wrong have been tried and found guilty and are going to be properly punished," Mr Cameron told reporters on his trip to the US.
"That is step one. But step two is obviously going to be the authorities - the police, social services, county council - everyone's going to have to ask some very searching questions about how this was allowed to continue for so long, and I know they are already doing that."
More top news
When you find yourself stuck in a vending machine, or for that matter a bottle bank, there are only a few people you can call.
Tuesday's weather for the east of the region
Tuesday's weather for the west of the region