Critics have said it would raise audit costs, but not improve audit quality.

Ernst & Young had no immediate comment, while PWC said there was no evidence that the radical measures would improve audit quality.

But mandatory rotation is opposed by companies and big audit firms, who said it would raise audit costs and would not improve audit quality.

Regulators in the United States and Europe have been exploring ways to improve audit quality since the 2007-2009 financial crisis.

Berson does not believe that mandatory auditor rotation, currently being considered by the Public Company Accounting Oversight Board, is the way to improve audit quality.

The agency's plan to improve audits shows it was meant to be completed by this September.

The Paris-based OECD has said Greece must make tax collection more efficient, improve audits and speed up court proceedings to strengthen enforcement.

In a statement attached to the PCAOB report, PwC said it had taken steps to respond to the concerns, including improving audit tools and training.