Les Lawrence, chair of the LGA children and young people board, today told delegates at the Association of Directors of Children's Services (ADCS) conference: "You need to do this to enable you to take the consequences of whatever the result is."
Lawrence also warned that children's services leaders would have to start defending their budgets to other local authority leaders as councils enter a period of tough negotiations on where to spend already stretched budgets.
"We need to challenge the concept of protection around budgets. We need to be able to justify what we are doing on the basis of sound strategic outcomes," he said.
He added: "We are going to have to take some hard decisions about disinvesting from things that don't show specific outcomes and a quantitative benefit. If it doesn't show this, we will have to say we can no longer invest in it."
Local authorities and their partners in the voluntary and research community plan to start evaluating services more robustly, to help directors of children's services defend their budgets.
Paul Ennals, chief executive of the National Children's Bureau, said he would work with local authority leaders to provide them with "killer facts" to help them commission services based on evidence.
"We need to work further and faster to get more evidence about what works," he said.
Peter Lauener, director of local transformation at the Department for Children, Schools and Families (DCSF) and soon to be chief executive of the Young People's Learning Agency, said that the DCSF and the ADCS will work together on a project to explore how best to secure resources for children's services.
But Andrew Flack, director of children's services in Derby, warned that local political power struggles can thwart attempts to protect vital services.
He said: "There is a distinctive difference between making the case in a stable local authority with strong political leadership and in a local authority where all three parties think they're able to win power. Then it becomes about who can be more macho about council tax."
