Maureen Cooper, director of Education Personnel Management, said the system appeared "ripe for fraud". Information requested on applications for criminal vetting forms includes bank account details.
"With access to a personal address, bank account details and information like a mother's maiden name, it would be very easy for someone to set up a credit card," she said.
"Everything that is being sent to the CRB is going to the same PO Box address in Liverpool. If you wanted to intercept that surface mail, it would not be difficult."
Like many personnel companies and authorities, EPM continues to be affected by delays at the CRB in processing the checks.
Although EPM sends approximately 300 forms to the CRB each week for schools in authorities including Cambridgeshire and Thurrock, it claims to receive between 40 and 50 back most weeks.
Ms Cooper said that the vast majority of applications were for school volunteers. She said councils were now encouraging schools to vet builders as well as visiting theatre companies.
The latest figures from the CRB show that 193,113 people are being checked - 83,106 have been waiting longer than the target three weeks.
A spokesman for the Home Office said there was no evidence that people who filled in the forms might be a target for fraud. He said: "We cannot carry out checks on people who will work with children and vulnerable adults unless we have all the details we need.
"Of course we are not complacent, but there are laws against intercepting post, and there are safeguards in place."
Graham Lane, education chairman of the Local Government Association, said it seemed unnecessarily apprehensive to fear that the bureau checks might be used by fraudsters.
But he added: "We have queried the number of details that are required. It seems that they are testing whether applicants could become members of MI5."
School standards minister David Miliband was quizzed by MPs about delays at the bureau during the education questions session in Parliament last week.
He agreed to look further into the reported problems, and said that a trouble-shooting team sent into the CRB by Home Secretary David Blunkett in September would be having discussions with a wide range of people about how the application process could be improved.
The CRB continues to contract out processing of forms to Madras, India, to help tackle its heavy workload. It has also begun offering education authorities a "fast-track" check for special cases they want vetted within 48 hours.