Children's rights campaign Article 39, which submitted the data request to Cafcass under the Freedom of Information Act, claims it is "implausible" that no child in care has had their human rights breached.
The charity submitted the request after becoming concerned that the law is not effectively protecting children and it has questioned the effectiveness of IROs, who should scrutinise and challenge the need for a care placement before a child is moved.
It is calling on Cafcass to carry out a review into how it is supporting the rights of children.
Article 39's actions follow a BBC Newsnight investigation, broadcast in the spring, which reported that the number of looked-after children aged 16 and over living in unregulated accommodation rose by 70 per cent in a decade.
- Fostering stocktake: six major recommendations for change
- Analysis: Streamlined system marks new era for safeguarding children
The homes are not registered or inspected by Ofsted and meanwhile police have raised concerns that they provide an easy target for gangs looking to recruit vulnerable teenagers.
Article 39 says that homelessness, separation from family members, out of area placements and treatment in the secure estate are among areas where children's rights could be potentially at risk.
"Parliament has empowered independent reviewing officers to involve Cafcass when local authorities are not fulfilling their obligations to children in care and care leavers," said Article 39 director Carolyne Willow.
"Cafcass in turn has been empowered to initiate legal proceedings on behalf of these children and young people, including when there has been a breach of their human rights.
"The data we've obtained strongly suggests these vital safeguards are not working. It's particularly implausible that no child in care has suffered human rights violations which warranted protective action by Cafcass.
"There's a lot of work going on by IRO organisations and partners to ensure children and young people get the protection from these posts as parliament intended.
"But it's now time for Cafcass to review whether it is properly acting for children in care and care leavers, and a fundamental part of this has to be a wholesale facing up to where the care system is not working, and why - whether this shows itself in the separation of siblings, homelessness and prison statistics, dependency on out of sight, unregulated provision and children sent many miles from home.
"These are all potentially serious human rights violations, which Cafcass - and actually the Children's Commissioner - should be actively and visibly involved in remedying."
IROs are appointed by local authorities to scrutinise children's care plans and take into account the views of the child.
A government-commissioned fostering stocktake last year suggested that councils could ditch the post but ministers later confirmed their appointment will still be a legal requirement, however, the nature of their role will be reviewed.
A Cafcass said: "Cafcass cannot take any action until an IRO has made a referral and for that reason we're unable to affect the number of referrals that we receive.
"We respond to every referral that we receive from an IRO and are obliged to appoint an officer of Cafcass (often the previous guardian) to provide an independent assessment of the circumstances.
"Following legal advice the Cafcass officer will recommend whether any legal action should be commenced in order to protect the child's interests.
"However, whether or not court proceedings are issued, Cafcass will continue to try and resolve any dispute by negotiation or mediation and to date most of the referrals have been resolved by agreement. In the majority of cases the local authority changed their decision.
"Claims under the Human Rights Act are not only made as a result of referrals to Cafcass but may also be independently pursued on behalf of the child by the child's solicitor.
"Children and the people who matter to them are at the centre of our work and it's our mission to provide a service that prioritises their safety, expresses their needs and leaves them in a better position.
"We will take every step possible to ensure a child's human rights are effectively protected and would not hesitate to take court action when there is no other effective way to achieve a positive outcome for the child."
A consultation on changes to children cases in the family court, which includes proposals for clarifying the IRO role as well as changes to Cafcass involvement in proceedings and special guardianship assessments, closes on 30 September.
The consultation, launched by Courts and Tribunals Judiciary, is considering responses from local authorities and social workers.