The couple were visited up to 20 times by social services

A report on the case said workers were "inappropriately optimistic" about the case involving Samuel Duncan and Kimberly Harte.

Duncan, 27, and 23-year-old partner Harte, were both jailed for kicking and scalding the four-year-old cerebral palsy sufferer.

They were sentenced to 10-and-a-half and 11-and-a half years respectively at Middlesex Crown Court.

The couple, from Maida Vale, London, admitted three counts of child cruelty.

Professionals were too adult-focused and believed the parents had worked hard to resolve their problems Ron Lock, Local Safeguarding Children Board

The little girl had boiling water poured over her hands, had huge clumps of hair ripped from her head.

She was also kicked so hard in the groin she suffered internal injuries, was locked naked in the toilet each night and forced to eat her own faeces.

The child had previously been placed in foster care, soon after her second birthday, following domestic violence in her home.

But in January last year, she was returned to her parents, despite concerns raised by her foster carers.

Ron Lock, who compiled the 53-page report for the Local Safeguarding Children Board said: "A more rigorous assessment process should have uncovered the poor relationship that would likely have existed between the father and his four-year-old daughter.

"An inappropriate rule of optimism existed in that professionals were too adult-focused and believed the parents had worked hard to resolve their problems."

But he acknowledged social workers from Westminster Council, who made 20 visits to the family home, could not have guessed the extent of cruelty being meted out to the girl as there was "no apparent sign of problems".

'Poor decision'

Child protection charities have also questioned judgements made in the case and urged people to be alert to signs of child abuse.

Michelle Elliot, of child protection charity Kidscape, said: "Because of a poor decision this child was handed back to her parents and harmed".

Wes Cuell, director for children and young people at the NSPCC, also said: "There are many children who continue to suffer severe abuse which is why everyone should look out for youngsters they believe are being ill-treated and take action to prevent it."

The girl's injuries have led to calls for a full independent inquiry into the council's handling of the situation.

The girl has now been placed in foster care, where she "is now thriving", said Julie Jones, chair of the children board.