Kenneth Palmer, father of 10-year-old Matthew who has Asperger's Syndrome, has been told by East Renfrewshire Council that he must undergo disclosure checks and pay for them himself if he wants to go on to his son's school bus and fasten his seatbelt.
He claims the parents of another child on the bus, who suffers from cystic fibrosis, also want to be able to belt in their child on "bad days" when her condition makes it difficult for her to use her fingers.
However, the council has said that only parents who have under-gone police vetting can board their contract buses.
Bus drivers are not allowed to fasten seatbelts - only supervise children while they do it themselves. But Mr Palmer says there are some days when his son is upset and needs him or his wife to reassure him when he gets on the bus.
Talks with the council led to the authority proposing that a rota of parents could be drawn up, allowing one disclosed parent to board the bus.
However, Mr Palmer said: "Why do we need disclosure when we are not being appointed to a post or position? All we are doing is an arrangement between family and friends."
A spokeswoman for the Scottish Parent Teacher Council, one of the strongest critics of the legislation on vetting and barring, said: "This whole process is completely outwith the scope of the legislation but is a classic example of how it is misunderstood and over-used, particularly by local authorities."
A spokesman for the council denied over-reacting.
"The parents have pushed this issue themselves and, as they want on the bus, we have to make sure they are disclosure checked, especially as they are dealing with children who are not their own. Parents would be entitled to demand that anyone fastening their child's seatbelt would have to be disclosure checked.
"Unlike SPTC, we run an education service, and our motto in relation to safety matters is to expect the worst and plan accordingly," he said.
The Scottish Executive said there was nothing in its Protection of Children (Scotland) Act stipulating that a parent had to be disclosure checked to go on to a school bus.