Councils are having to wait up to two and a half months to clear adults to work with children.
The Convention of Scottish Local Authorities has told Holyrood's inquiry into child protection that the failings of Disclosure Scotland are damaging services.
"Councils are faced with the dilemma of putting children at risk by employing people without full vetting information, or preventing vulnerable children from accessing services because staff-child ratios are not met.
This similarly exacerbates ongoing problems with recruiting foster carers and adopters," Cosla states.
Local authorities are pressing for services like education and health to take more of a lead in protecting children "rather than child protection being picked up largely through the traditional route of social workers working with vulnerable children and families".
Social work directors point out that while their staff come into contact daily with demanding families, "it can still be difficult to predict which ones will go on to seriously abuse their children. It is not an exact science."
Serious neglect caused by the "huge rise in children of drug-using parents" is placing ever greater demands on social workers. There are more referrals to the children's panel, more children on protection registers and more looked-after children.