An investigation has been launched into claims that councils are not allowing children in care their legal right to a say in decisions that affect their education.
The probe was announced last month by David Blair, head of the Scottish government's looked-after children unit, after he admitted that he did not know how many of the nation's 32 local authorities provided independent advocacy services.
Mr Blair said ministers wanted to ensure that every looked-after child had access to an independent representative, in order to end the current conflict of interest that means local authorities provide advocacy for access to services that they also pay for.
Under the Scottish government's Getting it Right for Every Child policy, all children are legally entitled to have their voice heard at proceedings, including children's hearings.
As yet, there is no obligation in law for councils to provide independent advocates at hearings, but ministers are legally committed to "considering" the introduction of that right under the Children's Hearings (Scotland) Act 2011.
Mr Blair made the pledge before the Education and Culture Committee in August, after bowing to pressure from members to find out how many young people were denied their legal right to express views on matters such as where they live and go to school.
He also came under fire over the ongoing failure to collate national statistics on which programmes improve the prospects of children in care - a year after the committee published a report calling for data as a "priority" to tackle the significantly poorer academic record of looked-after children.
Quizzing Mr Blair, committee convener Stewart Maxwell said: "The view of some people whom we have heard from is that the legal right to be heard that children now have is not being met by some local authorities.
"If that is the case, surely it is the government's duty to find out which local authorities are not meeting that legal duty and to deal with it?"
The Scottish government said it was talking to care charities about how best to introduce independent advocates to hearings.
Responding to the committee's questions on how widespread the breaches in advocacy rights were, Mr Blair said: "I do not know. There is a legal duty to hear the voice of the young person but we do not collect statistics on that.
"It has been put to me that at least one local authority has no advocacy. It would concern us if a legal duty was not being met; we would expect the inspection system to pick that up."
Defending the failure to compile a national database, Mr Blair said it had proved to be "considerably more complicated" than expected owing to the various ways in which information was recorded by public bodies.
West Lothian and Inverclyde councils confirmed that they both used their own employees (children's rights officers) instead of independent advocates, and they worked "at arm's length" to avoid potential conflicts of interest.
The developments follow a previous committee meeting in which Thomas Timlin shared his experience of the care system. He endured years of neglect, abuse and homelessness as he was moved from one family to another and was forced to repeatedly change school.
Mr Timlin, who is now 24 and a newly qualified social worker, said: "Throughout that process I did not have any advocacy. I did not have someone I could trust, who didn't have any agenda, whose only commitment was to me. I can't describe in words how difficult it is as a child when you have to move school."
A spokesman for local authorities body Cosla said: "Local government treats the views of looked-after children extremely seriously. Councils pursue a variety of ways of ensuring that looked-after children have access to advocacy services. We have not seen any evidence that councils are doing anything other than helping young people get their views across in as supportive a way as possible."