Steven Barker received a life sentence for the rape
One of the three people jailed over the death of Baby Peter has lost an appeal against his conviction for raping a two-year-old girl.
Steven Barker, 33, who was ordered to serve at least 10 years for raping the girl, was told by Lord Judge that he was "a danger to young children".
Barker, who was the boyfriend of Peter's mother Tracey Connelly, had claimed he did not have a fair trial.
But his challenge was rejected by the Court of Appeal in London.
Barker had been jailed for 12 years for causing or allowing the death of 17-month-old Peter Connelly in north London in 2007 at a separate trial.
But he claimed his conviction for the rape of the two-year-old girl was "unsafe".
Barker's QC, Bernard Richmond, had argued at a hearing in November that an Old Bailey judge should have halted the case against him.
An argument put forward to the appeal judges by Mr Richmond was that the evidence of the girl should have been excluded.
Baby Peter had more than 50 injuries when he was found dead
The trial judge, he submitted, should have ruled that the child was not a "competent" witness.
Lord Chief Justice Lord Judge said the child "was indeed a compelling as well as a competent witness".
He added: "On all the evidence this jury was entitled to conclude that the allegation was proved.
"Unless we simply resuscitate the tired and outdated misconceptions about the evidence of children, there is no justifiable basis for interfering with the verdict."
He said both Baby P and the rape victim, referred to only as X, were "exceptionally vulnerable by reason of their ages and the appellant's activity represented a gross breach of trust".
He added: "All the reports upon the appellant indicate that he is a danger to young children. He committed appalling crimes."
A spokesman for the Crown Prosecution Service said it was pleased with the judgement, adding the victim "demonstrated extraordinary courage".
"Those who abuse children should remember that their victims are not too young to help secure a conviction," he added.
Lord Chief Justice Lord Judge, Lady Justice Hallett and Mrs Justice Macur, also dismissed Barker's appeal against his sentence.
Baby Peter was found dead in his cot with more than 50 injuries, including fractured ribs and a broken back, at a property in Tottenham in August 2007.
Baby Peter's mother, Tracey Connelly, 28, of Penshurst Road, Tottenham, north London, and Barker's brother Jason Owen, 37, of Bromley, south-east London, were also jailed over the child's death.