Aylesbury child sex abuse: Barnardo's raised fears in 2008
Concerns about a girl repeatedly abused by a gang of men in Buckinghamshire were raised by a charity several years before the perpetrators were arrested, it has emerged.
Barnardo's told the BBC it had worked with the ring's two victims in 2008 and referred the case of one to the local authority and other relevant agencies.
The charity's Michelle Lee-Izu said "insufficient action" was taken.
Six men were found guilty on Friday of abuse on a "massive scale".
The Old Bailey heard the abuse in Aylesbury went on for years and involved rape and child prostitution.
Alcohol and DVDs
The court heard evidence from both victims, who came from troubled backgrounds and were befriended by the men who gave them alcohol, DVDs, food and occasionally drugs.
While aged just 12 or 13, one of the vulnerable girls, known in the trial as A, was passed between 60 mainly Asian men for sex after being conditioned into thinking it was normal behaviour, jurors were told.
Ms Lee-Izu, a lead director for child sexual exploitation, told BBC Radio 4's Today programme: "In 2008, we worked with both these young people and our work with these young women was very specific to them as individuals.
"We had concerns about the safety of one young woman and we made a referral to the local authority and the relevant agencies.
"At that time the agencies didn't respond in a way that we wanted, that we expected them to, although some actions were taken by the local authority so we escalated those actions further.
"But insufficient action was taken as far as we were concerned."
Girls 'let down'
Eleven defendants faced trial, accused of 47 sexual offences between 2006 and 2012 following an investigation launched in 2013.
Four were cleared of any wrongdoing, while the jury could not reach a verdict on one of the men.
The six who have been convicted will be sentenced in September.
Speaking on BBC Radio 4's Today programme on Saturday, David Johnston, director for children's services at Buckinghamshire County Council since 2014, said a review of the concerns raised by Barnardo's would be carried out to discover what happened and what action was taken.
He said: "Workers at the time missed a number of opportunities to perhaps protect them [the girls] or to provide other services for them. Having said that, we know a great deal more about child sexual exploitation and grooming now than we did back then.
"Over the time I have been in the post, we have reviewed a lot of practices."
He added: "Today, evidence of unhappiness shown by behaviour - such as school homework standards falling and running away - instead of being monitored as in the past, it is now investigated for motivation.
"More specialists are now working with local authorities and the police to build up knowledge of child exploitation to protect young people and those working with them."
On Friday, Mr Johnston apologised on behalf of Buckinghamshire County Council for "letting [the girls} down during this period in their lives".
He said: "We know a great deal more about child sexual exploitation than we did back then and I hope that young people who are worried about themselves or someone they know will have the same courage to come forward. We will do everything in our power to help them."