Protection for children at risk of physical and sexual abuse has deteriorated in Birmingham over the past year and is “inadequate”, according to a critical report into city council performance.

Education watchdog Ofsted found serious weaknesses in the way the council goes about safeguarding vulnerable youngsters.

Reports of children at risk are not being investigated quickly enough, there is not enough funding for family support and the council is taking far too long to complete serious case reviews into incidents where social workers are believed to have failed, the report states.

The findings reflect a sharp reversal in performance since last year, when Ofsted’s annual survey said Birmingham was delivering children’s services at above minimum requirements.

In 2007 the staying safe category, reflecting help for children at risk, was given a grade 2 ranking and classed as adequate. This year, the ranking has been reduced to grade 1 and is inadequate. Past improvements have not been maintained, Ofsted has warned.

The effectiveness of the children’s services category has been downgraded from good to adequate. Ofsted’s report follows intervention by children’s secretary Ed Balls, who ordered fresh reviews into whether Birmingham social services let down three children seriously hurt or killed. Mr Balls said the council’s original enquiries were unsatisfactory.

The council’s adults and communities department found itself under attack after the death in May of Handsworth seven-year-old Khyra Ishaq, who allegedly died of starvation. Perry Barr MP Khalid Mahmood called for an inquiry into why social workers failed to intervene.

Council leader Mike Whitby promised to work “in a positive spirit” with Ofsted and the government to raise standards.

Coun Whitby (Con Harborne) said he wanted to lead a national debate about the future of child protection.

Cases like those in Birmingham and Baby P in Haringey, London, who died after suffering more than 50 injuries despite being visited regularly by social workers, highlighted the need for a thorough review of what could reasonably be expected from social workers, he said.

Coun Whitby added: “We want to use the Ofsted report as a springboard. We are not interested in being ‘adequate’.”

Tony Howell, strategic director for adults and communities, said the council would “open the door” on social work.Mr Howell added: “We have a concern if the media continues to scapegoat social workers for the ills of society this will make an already chronic shortage worse.We want the public to know what kind of conditions people are living in, what their lifestyles are like and how we can help people move out of these terribly difficult situations.”