LONDON (AP) — A committee of British lawmakers says staff at some of the world's top accountancy firms are using insider knowledge gained while working for the Treasury to help private clients avoid tax.

The Commons Public Accounts Committee says Deloitte, Ernst and Young, KPMG and PwC should be barred from working for the government to stop the "ridiculous conflict of interest."

In a report released Friday, the committee said it had seen "cases of poacher, turned gamekeeper, turned poacher again, whereby individuals who advise government go back to their firms and advise their clients on how they can use those laws to reduce the amount of tax they pay."

The legislators say the practice makes it harder for the government to stop tax avoidance.