Speaking at a public services summit in London last week, Prentis said pitting providers against each other to bid for services was transforming the sector against its wishes.
He said: "For us, public services have traditionally relied on co-operation."
Several children's charities present at the summit said there were problems with the bidding process.Jenny Willmott, head of membership development at the National Council for Voluntary Youth Services, said: "It can be difficult for voluntary and community groups to compete in a commissioning environment."
Belinda Phipps, chief executive of the National Childbirth Trust, said: "We don't get the funding to find the time to put together a good bid. It's not something we would normally spend money on; we focus on service delivery."