The AM asked every council in Wales how many children were on its books who did not have an allocated social worker.

"The answers provide a snapshot of the position on a given day in Wales which was September 1 last year," he said. "The situation changes day by day as some children are allocated to social workers and others enter the system.

"I am worried about what my survey has revealed. Bridgend Council, which has had problems with its children's social services, had 120 unallocated cases - only Rhondda Cynon Taff was higher was 134.

"Yet, there were councils like Blaenau Gwent, Pembrokeshire and Newport which had no unallocated cases while others had just a handful so it's a pretty mixed picture.

"The fact remains that every day in Wales, there are hundreds of children who are either on the child protection registers, actually in care or classed as being in need who do not have a social worker allocated to them to provide protection."

Mr Cairns, who raised this issue with the minister at the Assembly this week, is calling for a full investigation by the Care and Social Services Inspectorate in Wales into how long children in Wales are waiting on average for a social worker.

"There has been a sharp increase in the number of children entering the system since the tragedy of Baby Peter," he said.

"There is a need for local authorities to be given additional resources from central government to ensure that no child again is ever treated like he was.

"Unless children have a social worker, it is impossible to know whether or not they are at serious risk. This is absolutely basic and we need to have more facts which a proper investigation will uncover."