The Children's Commissioner is launching a national inquiry into child sexual abuse.
The two-year inquiry will look at sexual abuse within the family environment including forced marriages since this often leads to child sex abuse.
Maggie Atkinson, the Children's Commissioner for England, said: "Society is rightly horrified by child sexual abuse.
"Most of our children are raised in secure, loving homes but I am sure very many of us will be disturbed by how much abuse within the family environment goes unreported and how little is done to support the children who suffer.
"As adults we are morally and socially obliged to protect children from harm. As Children's Commissioner, I also have a legal responsibility to promote their right to protection."
Questions of how widespread the problem is, what must be done to support the victims and how it can be prevented are to be investigated as a new report reveals alarming gaps and glaring omissions in the key knowledge needed to tackle the problem.
It is to build on the newly published report - It's a Lonely Journey - ordered by the Children's Commissioner which examined 57,226 research studies into child sexual abuse.
There is "almost no direct reference" to the child's experiences, which would help prevent other victims, and worryingly little is known about the prevalence of long-term psychological and physical harm, the report found. There was also almost nothing about the economic cost this places on society.
The researchers from Middlesex University also found that most support networks for child sex abuse victims who suffered within a family circle were created to help adult survivors rather than children.
The report also notes: "Despite research indicating that disabled children are around three times more likely to be victims than non-disabled children, they receive even poorer responses from professionals than non-disabled peers.
"Black and minority ethnic children are under-represented in child protection referrals, do not access child protection services with the same frequency as white children, or (when they do) may receive a poorer quality of support from professionals."
Research that is focused on the convicted male offender was identified as among the "key gaps" in the current literature on child protection.
It was also noted that there is "little evaluation research" addressing interventions for victims so it is difficult to identify the scale, nature and effectiveness of current work while there is international evidence which suggests that child victims prefer tackling the problem through group approaches.
The report also found some evidence efforts to help which focused on the family and not the individual child were more effective in addressing long-term impacts.
Centralisation of local services in one venue to cut the number of interviews with many professionals in many different sites and ensuring that children are fully informed about processes and their rights are some of the approaches to aim for, it was suggested.
Deputy Children's Commissioner for England and inquiry chairwoman Sue Berelowitz argues that "substantial" numbers of children are falling through the net because this type of "appalling and deeply traumatising abuse" is not being recognised.
She said: "Some studies suggest as many as one in 20 children and young people experience sexual abuse, the majority of it perpetrated by people within the family or family circle. We know that at any one time, around 43,000 children have child protection plans, only around 5% of whom are on a plan for sexual abuse. These figures do not add up."
The Office of the Children's Commissioner has vowed that "the experiences and voices of children and young people will be at the heart of this inquiry, and driving all that we do."
Report author Dr Miranda Horvath said: "Child victim-survivors' voices and first-hand experiences were absent from the vast majority of the research we reviewed for this rapid evidence assessment.
"It is imperative that future research and the work of the inquiry brings these to the fore using ethical but innovative methods, with the well-being of the child at the centre. At the same time, we need to know more about programmes that are focused on preventing family-based child sexual abuse before it occurs, in order to take a preventative rather than reactive approach."
Javed Khan, chief executive of children's charity Barnardo's, welcomed the inquiry, saying: " There are few crimes more abhorrent than the sexual abuse of children but when those perpetrating this vile act are relatives, people who are supposed to love and protect, it can be all the more harrowing."
He added: " Abuse within families is by its nature a hidden crime; easy to obscure from the authorities within the confines of a tightly knit unit.
"Shining a light on existing gaps in knowledge is vital if we are to support these children effectively and ensure robust procedures are in place to stamp out abuse."