The warning follows social workers in West Dunbartonshire raising repeated concerns over staffing shortages and overwhelming caseloads which has brought them to the brink of industrial action.
A statement issued by SASW said the use of sofas in emergencies has become more common in local authority residential units but usually only for one or two nights on a weekend.
"This kind of situation where a sofa is used for months at a time is unacceptable. Staff have acted appropriately in bringing this to the attention of managers and authorities.
"It is due to capacity issues with cuts in the number of residential places and private and secure residential places in Scotland being increasingly used to accommodate young people from England," it said.
Earlier this month, social workers within West Dunbartonshire, supported by Unison Scotland, voted overwhelmingly for strike action.
"We hope they get a fair hearing which leads to positive results for workers and for users of services. We are campaigning for improved working conditions in Scotland, which includes meeting with politicians and others who can influence better ways forward," SASW said.
"Ultimately, the funding constraints which are currently in place will not allow social workers to do the job they were trained to do," it added.
According to Unison Scotland there are almost 250 unallocated cases in children and families social work services across West Dunbartonshire.
The union said the situation was putting lives at risk and it had raised its concerns with the council on many occasions but no commitment had been pledged to deliver additional resources.
Simon Macfarlane, Unison regional organiser, said: "This is unprecedented, our members are at breaking point and the service is on its knees.
"Our members have lodged a collective grievance with the council over the poor service that children and families have been receiving, unacceptable workloads and staff safety.
"These committed staff are going above and beyond every day to look after some of the most vulnerable people in our communities - the fact is these people deserve better, and so do social work staff."
The union announced that a ballot for strike action held last week had been backed by 92 per cent of social work staff. The ballot of children and families social work staff recorded a turnout of 88 per cent.
A spokesperson for West Dunbartonshire Council said it was disappointed by the ballot result as a number of actions raised by staff had already been addressed.
"These include supporting staff to work in additional locations across West Dunbartonshire, recruiting additional social workers and agency social workers, allowing staff to carry leave over until June and paying staff for time off in lieu of more than 14 hours.
"We are hopeful of achieving a positive resolution for the families in our community who need our support most.
"While it would be inappropriate to comment on any individual young person, our staff and managers are dedicated to providing caring, nurturing home environments for all looked-after young people."