Ofsted, which came under fire after the Baby P scandal, has published its annual assessments of children's services in 147 local authorities. Last year, four councils were found to be inadequate, but this year inspectors found eight were lacking.
The number of councils which provide good or outstanding children's services has also fallen from 78% to 73%. Ofsted's data also shows that the number of councils found to be inadequate overall on all children's services, not just child protection, has also risen from none last year to four this year.
In a statement, Ofsted said the increase in inadequate ratings was "a cause for concern". Chief inspector Christine Gilbert said: "We see significant achievements across children's services and those involved in doing difficult work in complex circumstances can be pleased about their achievements.
"However, I am concerned that some services provided for the most vulnerable children and young people remain inadequate. "Where this has been found, we have clearly identified where improvements are needed.
We would expect those working in children's services to address these issues as an urgent priority with support from their local government office. "We will be inspecting next year to ensure they make good progress."
'Misleading' data-Earlier this month, MPs called for Ofsted to review the way it inspects children's services. The call came amid criticism that Ofsted inspectors had made "favourable" inspections of north London's Haringey Council, where Baby P died last year.
He suffered months of abuse while on the council's child protection register.A more thorough inspection this year revealed gross inadequacies in Haringey Council's child protection service. During a question session with MPs, Ms Gilbert admitted the inspection in 2007 was misleading because, she argued, her inspectors had been misled by Haringey's data.
Social workers' caseloads were heavier than had been reported and files were not closed as promptly as they should have been, she said.She told MPs she was writing to all council chief executives in England saying she expected them to vouch for the data their managers provided.
'Hands-on inspection' -Ofsted said it would introduce a new inspection system from next year. The so-called Comprehensive Area Assessment promises to "ensure a stronger focus on front-line practice, including annual unannounced inspection visits in every local authority".
Ofsted said the changes would be part of a "three-year, more intensive programme of inspection", introducing much greater scrutiny of councils where there were concerns about child welfare. But despite these assurances, the Commons Children, Schools and Families Select Committee is still planning to investigate the inspectorate.
Speaking to the BBC, chairman Barry Sheerman accused Ms Gilbert of being "complacent" and rejecting "out of hand" the committee's suggestions for improving children services departments. "I put it to her…. why didn't she embed, immediately, an inspector in each of them so that there was actually a real human being there, looking people in the eye, going out with young social workers on their difficult visits," he said.
"Really embedding them so it wasn't a paper-based inspection - it was a hands-on, really integrated inspection." Mr Sheerman said the "strains" placed on inspectors were clear as they tried to juggle responsibility for monitoring schools, nurseries and child protection.
"I think very often they are taking the kind of inspection system that is probably alright, but not wonderful, for schools across to children's services and it doesn't work," he added. Three of the 147 authorities Ofsted inspected are still contesting their grades.