The "horrifying death" of Baby P "could and should have been prevented" but social workers and other agencies were too concerned with keeping mother and child together, a second serious case review found today.
Social workers, doctors, lawyers and police should have been able to stop the situation "in its tracks at the first serious incident" but their outlook was "completely inadequate".
The 17-month-old boy, who was found dead with multiple injuries on August 3, 2007, should have been placed in care, the review carried out by Haringey Local Safeguarding Children Board found.
More should also have been done to discover the role and identity of the mother's boyfriend. Council workers denied any knowledge of the man even though Baby P's father warned them he had seen the boyfriend at the family home.
Although agencies thought it was unlikely the mother was injuring the child nobody took the next step and looked into whether somebody else was involved, according to the executive summary of the review which was published today.
Even after the boy, who can now be named as Peter, was put under a child protection plan, his case was regarded as routine "with injuries expected as a matter of course".
The professionals tasked with the boy's protection were "lacking urgency", "lacking thoroughness" and "insufficiently challenging to the parent".
Referring to the decision to remove a child into care, the review said: "There will be times when (professionals) have to grasp the nettle, using professional judgment, in the knowledge that they may be proved to be mistaken. Better that than the harm that the child will have to experience instead."
Graham Badman, the chairman of Haringey Local Safeguarding Children Board, said: "I believe the most important lesson arising from this case is that professionals charged with ensuring child safety must be deeply sceptical of any explanations, justifications or excuses they may hear in connection with the apparent maltreatment of children.
"If they have any doubt about the cause of physical injuries or what appears to be maltreatment, they should act swiftly and decisively.
"There are a number of points in this story as it unfolds where you could see care proceedings should have been followed - the thresholds were met.
"Much more attention should have been paid to the role of this man entering this vulnerable family.
"Baby P's horrifying death could and should have been prevented.
"The serious case review says that if doctors, lawyers, police officers and social workers had adopted a more urgent, thorough and challenging approach, the case would have been stopped in its tracks at the first serious incident.
"Baby Peter deserved better from the services that were supposed to protect him."
Mr Badman, a Government adviser and visiting professor at the University of London, said the manipulative and deceptive behaviour of the mother was "no mitigation" for social workers and agencies and it was important for them to use the "first-hand evidence of their own eyes" when dealing with such cases.
"Should more attention have been applied to the existence of the man? The answer is an unequivocal yes," he said, adding that there was "an enormous willingness" to believe the mother's stories.
"If you know or suspect that there are injuries that are non-accidental and you don't believe the mother is capable of doing it then there must have been somebody else."
He said every member of staff in the agencies involved with the case were "appropriately qualified" and "did what was expected of them" but they were operating on the assumption they could help the family by keeping them together.
He added that he thought the result of the review would be that agencies were more willing to "pick up the phone" to raise concerns.
The review was commissioned by Children's Secretary Ed Balls after Peter's death, after Ofsted found the first review published in November last year was "inadequate".
Haringey Council leader Claire Kober said: "This review clearly shows there were failings by all the agencies involved with Baby Peter.
"There were opportunities to help this family which should have been taken.
"I apologise for those failings."
Mr Balls appointed a new director of children's services, Peter Lewis, in December, and new senior staff are also in place.
Lynne Featherstone, Lib Dem MP for Hornsey and Wood Green, said: "The first serious case review either showed clear incompetence or was a cover-up.
"This one could not be more different from the first.
"It says exactly what we should have learnt at the start of this awful tragedy - Haringey Council, health professionals and the police all failed to protect Baby Peter from three individuals who set out to harm him."