Judith Gillespie, development manager with the Scottish Parent Teacher Council, says that the Scottish Executive is increasing the confusion among local authorities, schools and parents by declining to give precise definitions of which parents need checks.
The SPTC says it is being inundated with appeals for information from those snared by differences in interpreting the law on checking adults who work with children, brought in after the Dunblane murders. Some authorities order checks on all parents even if involvement is limited.
The Executive this week submitted its draft response to MSPs' child protection inquiry but immediately came under attack.
The parliamentary education committee, which is holding the inquiry, agreed on Wednesday to summon Disclosure Scotland, which has responsibility for the arrangements, on November 10 to answer a series of concerns.
Mrs Gillespie accused ministers of "running scared" as they struggled to define the limits of protection. "It's incompetent government. Either they pass or do not pass the legislation or they tell us what it means - but do not pass legislation on some vague risk to children.
"The biggest risks to children are not in public places but are domestic.
It appears from the Executive that every single adult who goes anywhere close to a child is a potential paedophile out to groom the child. Kids are becoming a no-go area.
"My message is, do not get involved until this is sorted out," Mrs Gillespie said.
She cited one parent of primary children in Aberdeenshire who has been forced to go through three separate checks as an exam invigilator, a children's panel member and now an active parent teacher association member. People "generous with their time" were subject to offputting and excessive bureaucracy while those who refused to accept checks were the subject of malicious rumours.
At another Aberdeenshire primary, some parents nearly walked out after being told about mandatory checks. One parent suggested sending out a form to every single parent.
Mrs Gillespie believes much of the Executive's plans for out of school sport, often involving volunteers, are at risk.
In its draft advice released this week, the Executive places the responsibility on authorities to agree guidelines for volunteer supervision but warns against "a blanket approach".
It suggests helpers with a limited level of contact or degree of supervision in place need not go through a check. That would include adults who help occasionally or act as a driver on an activity day trip when other adults are around and have been checked.
But the Executive advises that "care must be taken" to consider supervision in changing rooms, night-time care and personal assistance for disabled children.
The SPTC argues that most PTA activities fall outside the scope of the legislation.
Two authorities - East Renfrewshire and Aberdeenshire - demand police checks of all PTAs. "Should the system of police checks be properly applied to all PTA members, it would potentially involve some 1.25 million parents," the SPTC points out.
Some authorities are looking into checks on senior pupils aged 18 and over if they are involved in mentoring or support activities.
A further education college is said to have dropped courses for the rehabilitation of offenders because it has high numbers of school-aged students.