A child contracted gonorrhoea and chlamydia when she was aged 7 or 8 after she was abused by her foster father.
He 'breached the trust placed in him by sexually abusing her', social services said in a serious case review.
After several months living with her grandmother, she was placed with a couple named as Mr and Mrs George (not their real names) in 2012.
But the day after her first night in the placement, her school contacted social services to say that Claire had arrived for lessons 'walking splay legged' and complained that her privates were sore.
Teachers said this was unusual so they reported it, but social workers thought it might have been related to the sexual abuse she had suffered previously.
She had been given a child protection plan since she was a baby, due to concerns about drugs and alcohol abuse, domestic violence and neglect.
On one occasion, when Claire was four, she was found wandering in the street alone as she had been locked out of the family home.
Her birth family agreed to 'give her up to be cared for by the state' as they thought it would give her a better life. They said they were devastated and angry to hear what had happened to her.
Right from the start of her placement with Mr and Mrs George, there were warning signs.
As well as the report from her teachers, Mrs George told social workers she was finding it hard to cope. Within a week after she came to live with them, she asked for her to be removed from the placement, appearing distressed.
As the placement went on, things seemed to be improving, although Mrs George had counselling for panic attacks during the year and a bit Claire lived with them.
The truth emerged after Mrs George contacted their doctor to say Claire had soreness, asking for cream to be prescribed. The GP took swabs and contacted social services, concerned that she could have a sexually transmitted infection and that she was unsafe.
'A decision was taken to await the swab results before taking any other action,' a case review said. 'The (social services) manager informed the GP of this decision; the GP correctly told the manager she was extremely concerned by this response and went on to make numerous phone calls to health colleagues in an attempt to elicit a different response.'
The lack of swift action 'left Claire at risk of harm and fell well below expected practice,' a review found.
Sarah Baker, CSCB Independent Chair, said: 'Claire's' foster carer breached the trust placed in him by sexually abusing her. On behalf of the Croydon Safeguarding Children Board I want to express the deep sadness we all feel for the terrible experience Claire and her family subsequently went through.
'Staff have been fully engaged with the Serious Case Review. All, without exception, believed at the time of this incident they were providing Claire with a safe and secure home.
'The review found no evidence that anything at the time could have indicated this foster carer was likely to sexually abuse a child in his care.
'However there are still lessons to be learned and actions were immediately taken to tighten up a variety of processes. Staff have also received additional training and guidance to increase their awareness and understanding. I will ensure the findings from this review are built into our future action plan.
'Claire is doing well with her new foster carers, despite this horrible experience and continues to enjoy the unconditional support of both them and her family. On behalf of the Board I wish her all the very best for the future.'
Social workers didn't act immediately because as Claire was spending alternate weekends with her family, they thought she could 'have been infected by someone outside the placement, or that the infections had remained dormant from when Claire had been sexually abused whilst living with her mother.'
It took five days before Claire was taken to an emergency foster placement, after the test results came back.
Social workers didn't contact her grandma, who had been (wrongly) told by Mrs George that Claire had been diagnosed with thrush when she asked about her soreness.
'The reaction of Mr and Mrs George to the information that Claire had sexually transmitted infections was one of anger,' the review said. 'Mr George became particularly angry and abusive; Claire witnessed this anger and was distressed.'
At a later date her foster mum Mrs George tested positive for gonorrhoea and Mr George tested positive for chlamydia.
It was felt that Mr George could have received treatment for gonorrhoea before the test was done.
Social workers blamed him for Claire's infections.
Claire has now moved to live with specialist foster carers and remains in this placement to date where she is said to be doing well.
Source - Metro