Some 40,000 children are in the care of drug users or alcoholics

Social work directors said checks took up a lot of time and there was a "temptation" to appoint people early to avert a staffing crisis.

Local authority group Cosla said some people were recruited before checks.

Social work directors have also warned of an exodus of experienced staff from child protection work.

Child safety in the UK was placed under the spotlight following the murder of Soham schoolgirls Holly Wells and Jessica Chapman in 2002.

Ian Huntley was given the all-clear by Cambridgeshire Police to work as a caretaker and the school where he worked failed to check his references.

The temptation is to say that we will simply start this person on a temporary contract prior to receiving (checks) Alexis Jay ADSW

Alexis Jay, vice-president of the Association of Directors of Social Work (ADSW), told the Scottish Parliament's education committee that it took eight to 10 weeks for criminal checks to be completed.

She said: "The temptation is to say that we will simply start this person on a temporary contract prior to receiving it and then move to a permanent contract when the check comes through.

"I must emphasise that I don't have any evidence that this is happening. It has in the past but everyone is increasingly vigilant and it's less likely.

Children's Charter

"Nevertheless, if you are pressed it could potentially lead to that."

Cosla's social work spokesman Eric Jackson said people were being employed before checks were completed.

But he added: "In certain circumstances they (councils) would employ people but they would not be given front-line responsibilities to work with young people, for example, until these checks have come back."

Jack McConnell wants services to liaise effectively

First Minister Jack McConnell's "Children's Charter" spelt out the need for co-ordination among social workers, the police, health and education services.

It sought to improve the identification of children at risk of abuse and follow up on their cases.

Official estimates suggest that 40,000 children are living with adults misusing drugs or alcohol and funding has been made available to train an extra 300 social workers.

But the ADSW has said that, despite executive assurances that more posts have been created in areas dealing with children, most are for projects involving less individual case work.

A report for the association said: "Scottish Executive statistics suggest that the number of social workers in posts has grown.

'Impossible' workloads

"These posts are mainly in new initiatives such as community schools, youth justice and early intervention projects... (and) have lured social workers out of child protection.

"This means that child protection work is now dominated by large numbers of inexperienced social workers with the few remaining experienced staff carrying impossible workloads of complex child protection cases."

Meanwhile, a social work conference in Glasgow has heard union calls for a comprehensive review of social care in Scotland.

Unison has also proposed a new standing system for child protection case inquiries to ensure consistent approaches to investigations into deaths or other incidents.

Edinburgh branch secretary John Stevenson, himself a child protection social worker, said: "No service can operate with 40-50% shortfalls in staffing, which is not unusual in child protection across Scotland."