Annette Brooke, Lib Dem children's spokesperson, told delegates at a fringe meeting at the party's conference in Bournemouth, that families sometimes have trust issues with social workers.
"There are so many issues where the public doesn't trust social workers," she said.
"People are less willing to approach social workers because they think their child may be taken away.
"There is a possibility of the voluntary sector stepping in and providing services because people are more willing to access them."
Brooke said Home-Start, which currently has 16,000 volunteers visiting families in their own homes to offer support, friendship and practical assistance, is a good example of the work the voluntary sector can do.