The committee said that the tax authority received 79 million calls in 2011-12 about issues such as self-assessment forms, but 20 million of these calls were not answered.
The ICAEW lists a whole range of potential problems with the current plans, from possible breaches in confidentiality to the prospect of making half a million more people fill in self-assessment forms than currently have to.
Those affected will need to fill out self-assessment tax forms for the current financial year - starting in April - to show they still qualify for the payments.
Under heavy pressure from unions to rule as it did, the administration made its decision following a Labor Department assessment that public sector work, from cleaning streets to processing government forms, qualified as work under the Fair Labor Standards Act.
"CIE is committed to working in equal partnership with our colleagues from education ministries around the world, a relationship that forms the backbone of our reputation and work in global education provision and assessment, " he said.