The US Securities and Exchange Commission is to charge PwC, KPMG, Deloitte, Ernst & Young and BDO, for violating its Sarbanes-Oxley Act (SOX) on account of the firms' refusal to provide audit work papers and other documents relating to China-based companies listed in the US.

The move follows months of wrangling during which the SEC has asked for audit working papers to support its investigation into Chinese companies which it suspects of using fraudulent accounting.

The SEC said that the audit materials concern nine China-based companies which are listed in the US and audited by the five firms.

Robert Khuzami, SEC division of enforcement director, said that the SEC could only test the quality of the underlying audits and protect investors from the rsik of accounting fraud if it had access to the working audit papers from the auditors.

'Firms that conduct audits knowing they cannot comply with laws requiring access to these work papers face serious sanctions,' said Khuzami.

The SEC has also taken more far-reaching action, deregistering nearly 50 companies and filing fraud cases against more than 40 foreign issuers and executives through the work of a crossborder working agency.

Earlier this year, the SEC announced proceedings against Shanghai-based Deloitte, which similarly refused to provide documents to assist the SEC in its investigation of a China-based client. The proceedings relating to Deloitte in that instance continue.

In the latest case, an administrative law judge will be expected to schedule a hearing to determine remedial sanctions against the firms.