The group said that the new system, which sees families with one parent earning over £50,000 having their benefit taken away, undermines the idea of individual taxation, with money being taken away from one person and given to another. The ICAEW have sent a report to Treasury MPs.
New benefit rules are set to be introduced in January, affecting more than a million families, although the finer details of how it will be implemented is still being worked out.
Speaking in The Daily Telegraph, the ICAEW said, "Families in similar financial situations could be treated quite differently, undermining the policy's fairness objective and creating very high marginal rates of tax for some.
"Taxpayers could find their tax confidentiality breached and experience lower service standards while grappling with an even more complicated system. Their confidence in HMRC and the tax system will be undermined and there will be behaviour changes and planning to avoid the charge."
Labour meanwhile voted against the change as it says new legislation is a mass, but they have not yet committed to reversing the changes if they win power.