Up to 371 families with 803 children were living in emergency accommodation in Dublin last month.
According to Barnardos this represents a 40% increase on last June when the Dublin Homeless Executive began tracking the number of families in emergency accommodation.
The organisation says that sometimes parents have to leave their children in care because they are unable to secure appropriate housing.
It also cites one case where a child could not get onto a waiting list for an operation because he did not have a permanent address.