Refco, the futures broker that is the subject of an SEC fraud probe, was still not Sarbox compliant when it raised $583m (£333.4m) on the New York Stock Exchange in August.

In the prospectus issued before its listing, Refco admitted that it would be exposed to risks relating to the evaluation of its internal controls as required by section 404 of the Sarbanes-Oxley act, which was introduced in 2002 to prevent corporate scandals such as Enron and WorldCom.

Refco said at the time that it was confident of achieving Sarbanes-Oxley compliance by the deadline of 28 February, 2007.

It added, however, that it was still 'in the process of evaluating, testing and implementing internal controls over financial reporting' and did not have the actual controls in place for auditors Grant Thornton to attest to.

This could protect Grant Thornton from an auditor liability charge, as there were no internal controls in place to audit prior to the news that Refco CEO Phillip Bennett may have been involved in a $430 (£245m) fraud.

In a statement Refco said: 'We cannot be certain as to the timing of the completion of our evaluation, testing and remediation actions or the impact of the same on our operations.

'If we are not able to implement the requirements of Section 404 in a timely manner or with adequate compliance, we may be subject to investigation and sanctions by regulatory authorities, such as the SEC and the NYSE.'