The number of children considered at risk of harm increased by a third in the two years after Baby Peter's death, but social worker numbers only rose by 10%, a survey has found.
Investigations into possible abuse or neglect of youngsters soared by 20.3% between the last quarter of 2007 and the same period in 2009, according to research for the Association of Directors of Children's Services (ADCS).
There were 32% more emergency protection orders, used when there are concerns that a child is in immediate danger, and courts granted 38% more interim care orders to give local authorities responsibility for children's well-being.
Over this two-year period, following Peter's death in August 2007, 32.9% more youngsters thought to be at risk of harm were made subject to a child protection plan.
The number of cases where children were brought to the attention of social workers by the public or professionals rose by 24.6%, and those judged likely to need further investigation increased by 16.5% but the 105 councils surveyed said staffing levels - including managers, social workers and assistant or administrative staff - went up by only 10%.
Marion Davis, the new president of the ADCS, which represents directors of children's services and their senior managers in England, said the findings showed the pressures faced by local authorities.
She said the rises appeared to have begun before full details about the horrific case of 17-month-old Baby Peter - now named as Peter Connelly - came to light in late 2008.
She said: "It is clear from the 10% increase in staffing that councils are aware of increasing pressures and are taking steps to increase the number of staff dealing with child protection concerns, but that councils have not been able to keep pace with the dramatic rise in demand.
"The rises are in every part of the system, from the front door to the family courts, and we believe this shows that this is not a knee-jerk reaction to high profile cases, but rather that agencies are getting better at identifying those children who require extra support."
Peter died at the hands of his mother, her lover and their lodger in Tottenham, north London, on August 3 2007 despite being on the at-risk register and receiving 60 visits from social workers, doctors and police over the last eight months of his life.