Police failed to properly investigate allegations of sexual abuse in Nottinghamshire children's homes, a former senior social worker has said.
More than 100 complaints of abuse have been made since investigations began in 2010.
But, the social worker said reports she made in the 1990s were not believed because of the children's backgrounds.
Police and Crime Commissioner Paddy Tipping said: "Historically, victims haven't been listened to enough."
Mr Tipping, who was himself a social worker in Nottinghamshire in the 1970s, was interviewed as a witness in December.
Speaking to BBC Radio 4's Today Programme, the former social worker - who wished to remain anonymous - said she made three complaints as recently as the early 2000s after children disclosed sexual abuse to her.
"The difficulty that we had was that the residential staff would deny it. They would provide alibis for each other," she said.
"The children or the young people: where were they going to go? Even if we moved them... the staff moved around."
Actress Samantha Morton, who spent much of her childhood in care homes in Nottingham, said she was sexually abused by residential care workers as a teenager.
Golden Globe and Bafta winner Ms Morton, 37, said she was abused at the now-closed Red Tiles children's home in Bulwell, one of the homes under investigation by Nottinghamshire Police.
She later moved to another home, Wollaton House, where she said she was physically abused.
- The force's investigation, Operation Daybreak, which has seen 11 people arrested, has centred around the Beechwood care home in Mapperley
- It has since widened to include 12 other homes across Nottinghamshire and Derbyshire
- More than 100 complaints of abuse have been investigated, dating back to the 1960s
- The force said it was "one of the largest" criminal investigations in its history with potentially more than 150 abusers
- Actress Samantha Morton claimed in September 2014 she had been abused at Nottinghamshire care homes as a teenager. She was due to speak to police in October
- PCC Paddy Tipping, a social worker in the 1970s, was interviewed as a witness in December
- Information from an FOI request in May 2014 revealed the city and county councils had paid £250,000 in compensation to 26 former residents and a "significant" number of other claims were being considered
The investigation has centred around the now-closed Beechwood care home in Mapperley but has since widened to include 12 others across Nottinghamshire and Derbyshire.
The force said it was "one of the largest" criminal investigations it had ever undertaken with more than 100 victims and potentially "more than 150 abusers".
Supt Helen Chamberlain, head of public protection, denied police were overwhelmed by the scale of the inquiry.
"What's emerging today is a very complex scenario where we have a number of allegations made by over 100 people quite often more than 30 years on," she told Radio 4.
"Much of the information recorded at the time has been destroyed and some suspects have died."
She said that in some cases where police had been accused of failing to act, interviews had been carried out at the time but not enough evidence was found to continue the investigation.
Responding to the accusation by the former social worker that officers used derogatory terms to describe children from poorer areas, Supt Chamberlain said she could not condone misconduct but the force had "moved on significantly in recent years".
She has called on the former social worker to contact police so she can help with their investigation.
In a joint statement, Nottingham City Council and Nottinghamshire County Council, which ran Beechwood and other homes involved, said they were "frustrated" an independent review could not start until after the criminal investigation.
"Survivors of child abuse can be assured that we are supporting the police investigation to try and get to the truth and hopefully bring any perpetrators to justice."