Accountancy firms have emerged as surprise long-lasting beneficiaries of the Sarbanes-Oxley Act, as US-listed companies have been forced to pay their auditors larger fees to comply with the tough corporate governance rules, according to a new study.

The findings, in a report by law firm Foley & Lardner, confound predictions that US companies would only face a one-off increase in audit fees and other costs as a result of the legislation, introduced after the Enron and WorldCom scandals.