More than half of councils are failing to protect the nation's most vulnerable children, a damning report has found.

The standard of child protection at one in seven local authorities is "unacceptably poor", Ofsted has warned.

A new report by the watchdog concluded that too often child protective services are "manifestly and palpably weak."

Ofsted, which inspects children's social care, found that 20 of England's 152 local authorities have "inadequate" safeguarding measures in place to protect children at risk of abuse or neglect.

Just 3% of councils were rated as "outstanding" and 86 - more than half - were deemed to be "less than good".

Birmingham City Council, one of the 20 to be classed as "inadequate", has now failed on seven inspection judgements, Ofsted said.

HM chief inspector Sir Michael Wilshaw called England's second city a "national disgrace".

He said: "Why is it that nearly a third of children in the city live in households on low incomes? Why is it that infant mortality is almost twice the national average, worse than in Cuba and on a par with Latvia and Chile?

"They must surely be linked to the evidenced failure of corporate governance on a grand scale - governance that has failed to grasp the nettle over many years and which has relegated our second city to fourth division for children's services.

"These are shocking statistics and a national disgrace."

He implied that the council would work better to protect children if it was smaller, saying: "As somebody said about the banks not so long ago, if they are too big to fail, they are too big. The same could be said about this council.

"It is an absolute disgrace and government needs to look at this with real urgency. If better governance means breaking it up so that children are better protected, then that's what needs to happen."

In its first stand-alone social care annual report, Ofsted said that children's services need "strong and stable leadership" to improve the services that provide help, care and protection to at-risk children.

I nspectors found that in the weakest places many "basic acceptable practices" were not in place and some authorities were criticised for poor coordination with health workers, police and schools.

Sir Michael called on the Government to review the role of safeguarding boards - which are made up of key agencies such as police, probation, youth justice, heath, education and social care workers - to ensure local safeguarding of children is effective.

He said: " Too often, inspectors arrive unannounced in councils only to see child protection that is manifestly and palpably w eak.

"Typically, these are the councils where case files of individual children demonstrate inadequate intervention; where referral thresholds are loosely defined, and where safeguarding boards aren't worth the name."

He also called for more clearly defined protection plans so that they clearly set out what actions will be taken against families as a consequence of their actions.

"I would like to see firm, authoritative action taken with struggling families across our social care system: tough but empathetic responses to parents who expect their children to live with the daily consequence of their violence, protection plans where the things that must quickly change are clear and the consequences of failing to act are obvious," he said.

Parents must be challenged "to shoulder their familial responsibilities", he added.

The report highlights that across England 700,000 children live in a home with an alcoholic parent, 100,000 children have parents who are being treated for a hard drug addiction, 130,000 live in domestically violent homes and there are 17,000 children living with a parent who has a severe or enduring mental illness.

Sir Michael also called for "better joined-up thinking" across local government after he raised concerns that bookmakers and fast food shops do not help troubled families.

He said: "When we go to some of these areas, why do we have so many betting shops? Why do we have so many fast food outlets? Why do we have so many games arcades in areas which actually do not help to support troubled families and troubled children. Why does that happen? It's not just joined-up thinking in social services, it is joined-up thinking across government."

Debbie Jones, Ofsted's national director for social care, added: "The picture of performance we are publishing today shows there is clearly an ongoing need for improvement.

"Some services are increasingly expert at reducing risk, helping families to look after their children and enabling children at risk in their area to make good progress.

"It can be done, and therefore it must be done in all areas, equally well. Ofsted will be rigorous in holding local councils and social care providers to account but we will also support them to make the improvements that children deserve."

A Birmingham City Council spokesman said: "We are already on record as saying that we have failed to meet the basic expectation of keeping vulnerable children in this city safe.

"This is a long-standing problem which we acknowledge and the leader has said that improving children's services is his number one priority.

"While we can only agree with the seriousness of what Sir Michael has said with regard to children's services - indeed we have said it ourselves - we now need improvement rather than further diagnosis lacking any offer of solutions.

"We must work with Ofsted on this and we repeat our determination to improve the safety of children in this city as the highest priority for this council."

A Department for Education spokeswoman said: "Ofsted's report is helpful, and when their more rigorous inspection regime identifies that councils are failing to protect children, we are taking action.

"There is no quick fix and we must be assured any progress is embedded and sustained - effective management is vitally important.

"Ofsted's focus on the quality of local safeguarding children boards is welcome.

"Their new inspections will help strengthen the role of l ocal safeguarding children boards and ensure they are effective."

Andrew Webb, president of the Association of Directors of Children's Services, said Ofsted's inspection methods were "not good enough" to measure the performance of councils properly.

He told BBC Radio 4's World at One: "We have one of the safest countries in the world to grow up in, relatively low levels of child death. We have a very responsive system."

But he said: "Ofsted has painted a picture using language which is, frankly, unhelpful. They claim they can judge in a single word whether a local authority is inadequate, requires improvement or good.

"What they are talking about is really complex systems, and in any complex system dealing with human beings there is bound to be variation.

"I think their methodology is seriously wanting. The methodology they use is not good enough for them to be able to say, in a single word, 'this is an inadequate authority'."