The Manifesto Club, a pressure group formed by journalists and academics, has started an online petition against the Bill, which it claims will see one-third of the adult working population subject to criminal records checks.
The petition received 300 signatures in three days when it was launched last week. The group claimed "a significant number" of them were from members of the voluntary sector.
One of the group's founders, journalist Josie Appleton, has written a report to coincide with the launch, warning that the Bill could push an already overloaded Criminal Records Bureau to breaking point and further deter volunteers.
"Volunteers are being put off by unnecessary CRB checks," she said. "The system is an insult to people who have offered to give up their time for free, only to be treated like criminals."
She added: "The checks are more about people covering their own backs. There's no real evidence that they protect children."
Mark Restall, head of communications at Volunteering England, agreed that unnecessary checks were being carried out.
"Too many checks are being carried out at the moment because people are panicking about liability and aren't really sure who needs to be checked and who doesn't," he said.
But the NSPCC disagreed, arguing that the system is essential to safeguard children. A spokeswoman said: "You need vigorous vetting and barring procedures to stop individuals who mean to harm children from volunteering or working alongside young people. However, the NSPCC recognises that checks alone are not enough to protect children.
"Vetting and barring will be effective only if it is combined with other preventive measures and a culture of vigilance from everyone."
A spokeswoman for the CRB said: "The fact that there's been an increase in the number of CRB checks shows the importance placed on them. We wouldn't argue for less protection for children and other vulnerable groups."
- The Manifesto Club, a pressure group comprising journalists and academics, has started an online petition against the Safeguarding Vulnerable Groups Bill
- The petition received 300 signatures in three days when it was launched last week
- The club fears the Bill could push the Criminal Records Bureau to breaking point.