Children with learning difficulties are at increased risk of sexual exploitation, according to new research.
A report commissioned by Comic Relief suggests those with disabilities faced "additional barriers" to support than other children.
Youngsters with learning disabilities were more vulnerable because they were disempowered and socially isolated and also had a lack of access to sex and relationships education, the researchers said.
The charities behind the report, including Barnardo's, the Children's Society and the British Institute of Learning Disabilities, called on the Government to improve sex education and also warned that professionals lacked the understanding and training needed to deal with child sexual exploitation involving those with learning difficulties.
The researchers said the report "illustrates that the abuse of disabled children is under-reported and often hidden", while also highlighting "that disabled children often make clear disclosures of abuse - often multiple disclosures - without being heard".
Barnardo's chief executive Javed Khan said: "No-one wants to believe a child with learning disabilities could ever be exploited in this way, but it is happening all over the UK.
"A lack of awareness of the needs of these vulnerable children is playing into the hands of perpetrators of sexual exploitation.
"Professionals working with children must get training to recognise the risks faced by children with learning disabilities and help them to stay safe."
There were, the report said, "false perceptions" that youngsters with learning disabilities did not have the same relationship needs as other children or that they could not be sexually exploited.
An analysis of prevalence studies from around the world, including the case records of 50,000 of young people in Nebraska, in the US, suggested those with learning difficulties were around three to four times more likely to be abused.
But the amount of data available on the abuse of disabled children in the UK was "poor", meaning victims were generally "invisible".
The report, entitled Unprotected, Overprotected, said: "Young people with learning disabilities share many of the same vulnerabilities to CSE (Child Sexual Exploitation) that are faced by all young people, but there is evidence to suggest that they are more vulnerable to CSE than their non-disabled peers.
"The evidence also illustrates that this group of young people face additional barriers to their protection, and to receiving support if they are at risk of, or have experienced, CSE.
"The reasons for this are complex and appear to be entrenched in the way society perceives and treats young people with learning disabilities.
"To address and prevent further exploitation requires fundamental change in societal attitudes and approaches to how young people with learning disabilities are treated and supported in the UK."