Children as young as seven are being placed in children's homes in one local authority due to a lack of available foster parents, MSPs on the Welfare Reform Committee were told.
Council officials were at the committee to discuss the impact of welfare reform on children's services.
Increased pressure on families as a result of benefits changes could result in more demands being placed on social care and health services, they told the committee.
Labour MSP Margaret McDougall asked about the effect on fostering services.
She said: "If there is this huge increase on the pressures on the parents, is that support there to help the children?"
Stephen Brown, of North Ayrshire Council, said: "We have certainly had an increase on the pressures on our fostering service as a result of an increased number of children being accommodated.
"We have had the unfortunate situation where we have had to house some children in some of our units at an earlier age than we would ordinarily like.
"So, some of our children's houses have accommodated children as young as seven or eight, which is far from ideal, because of an absence of appropriate foster placements."
Richard Gass, of Glasgow City Council, said the local authority was running a "continual campaign" to recruit foster parents.
He said economic circumstances may be preventing some people from signing up.
"Perhaps the economic climate is a barrier to folk coming forward," he added.
Alistair Gaw, vice president of Social Work Scotland, said that in Edinburgh alone there are 1,000 children in foster homes, children's homes and living with kinship carers.
"We continually struggle to find enough foster parents," he said.
"There is definitely a need for more foster carers in the country, there is no doubt about that."
Mr Gaw said there had been attempts to increase the number of children cared for by kinship carers - other family members, such as grandparents.
"I think one of the problems we have is that some of the impacts of the changes to the benefits system are actually having a negative impact on kinship carers," he added.