A sister of Baby P, the 17-month-old boy killed while under the protection of Haringey social services, was allegedly seriously abused despite also being on the council’s “at risk” register.

The girl and Baby P, who died in August last year at the hands of his mother, stepfather and a lodger, had both become subjects of child protection plans eight months earlier.

Baby P was found dead in his blood-spattered cot with multiple injuries including fractured ribs and a broken back. He had suffered months of physical torture but social workers and other officials failed to save him despite more than 60 visits. It has now emerged that Baby P’s sister was also allegedly subjected to serious abuse. Legal restrictions prevent further details being disclosed.

The job of Sharon Shoesmith, head of children’s services in Haringey, was in the balance this weekend with ministers privately describing her position as untenable. An inquiry began last week into child protection in the borough.

Ed Balls, the children’s secretary, has accused the council of breaching government guidelines on child protection and is furious at the failures. Shoesmith has not apologised and says there is no need for resignations.

Balls said yesterday: “I am angry that crucial interventions to save this little boy were not made. Professionals working with children do a tough job in very difficult communities but I will not hesitate to act on the findings of the investigation.”

Baby P’s mother, her boyfriend and a lodger, Jason Owen, were convicted of causing or allowing his death. On Friday a judge told the trio that they should expect substantial prison sentences.

Shoesmith and officials at Haringey council have repeatedly cited an initial inquiry into Baby P’s death as evidence that they were not to blame.

One of the authors of that report, Fergus Smith, an independent consultant, admitted this weekend that his inquiry was of “limited value”. He said he had been given no independent access to documents or staff for his investigation.

He also said that a panel chaired by Shoesmith had met him to agree the content of the report before it was published last week, but insisted that the document was not a “whitewash”. He said it had limited value in the light of the criminal trial. “There has been further and pretty worrying information that has emerged from the criminal trial,” he said.

The public outcry over the death of Baby P and the inability of Haringey social services to prevent it has triggered a government inquiry into the running of the department, jointly conducted by Ofsted, the Healthcare Commission and HM Inspectorate of Constabulary.

A spokesman for Haringey council refused to comment on its conduct relating to Baby P’s sister.

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