Difficulties in recruitment and retention, the lack of priority given to the issue, inadequate resources - especially for area child protection committees - are some of the factors hindering service provision.
The report, Safeguarding children, commissioned by the government, was conducted by eight public sector inspectorates including the Social Services Inspectorate, Ofsted, the Commission for Heath Improvement and HM Prisons Inspectorate.
It has gone to home secretary David Blunkett, health secretary Alan Milburn and education secretary Estelle Morris for consideration.
Local agencies interpreted their safeguarding responsibilities in different ways with different emphasis.
The report said: 'Many staff from all agencies were confused about their responsibilities to share information about child welfare concerns with other agencies.'
It added: 'There were few formal agreements between agencies about how and when information should be shared.'
Inspectors also found a lack of effective leadership in area child protection committees. Local agencies had varying levels of commitment to them and generally did not accept they were accountable to the committees for safeguarding arrangements.
Concern was noted about the many agencies placed under pressure because of difficulties recruiting and retaining skilled and experienced staff and the lack of resources available to improve services.
Owen Davies, Unison's deputy head of local government, said: 'The report confirms what we have been saying for years. There is a huge problem of recruitment and retention in social work which leaves vulnerable people at risk.'
He added: 'We know that one of the contributing factors when things go wrong is that agencies don't communicate with each other. We need to strengthen the ACPC system to ensure no agency can let down the others by failing to participate fully in joint work or by failing to share important information.'
Recommendations included considering whether ACPCs and multi-agency public protection panels should be established on a statutory basis to ensure accountability, authority and funding. There should also be adequate support for local agencies to recruit and retain sufficient levels of qualified staff.