Judge John Gower criticised police and social services for failing to take sufficient notice of neighbours who had complained about the girl's condition.
Sophie Merry died from ruptured intestines after being hit by her stepfather, Lewes Crown Court was told. A pathologist later found more than 170 bruises on her body.
Kathleen Merry, 23, and Kevin Strudwick, 29, her former boyfriend, were both convicted of manslaughter and cruelty. Strudwick was jailed for 15 years and Merry for 10 years.
'It is a most disturbing state of affairs and I hope the responsible authorities, the police, social services and even possibly the Department of Health, will make sure a thorough, searching and full inquiry is instituted into how this deplorable situation came about,' the judge said.
Camden Pratt, QC, for the prosecution, said Sophie had been subjected to four months of abuse after her mother moved into a cramped caravan with Strudwick at Selsey, near Chichester, West Sussex.
The relationship started while Merry's husband, John, was awaiting trial for the murder of a young woman in Littlehampton, West Sussex. He was later convicted and jailed for life.
Mr Pratt said other caravan dwellers became concerned at Sophie's condition and called the police two weeks before her death. Officers visited but left after accepting that Sophie's black eye had been caused by her brother Tony, aged four.
Det Supt Graham Hill, of Sussex Police, said later: 'It is a question of judgement. The officers, with the information that they had that night, made a judgement that the explanation given was acceptable.'
A spokesperson for West Sussex social services said Sophie had been visited five times in the months before her death and always appeared happy and well. He death was 'a matter of deep regret and procedures will now be reviewed following a full investigation which has taken place'.Reuse content