Public companies can expect some extra scrutiny of their internal control over financial reporting in the upcoming audit cycle after regulators gave auditors a new warning to fix lingering problems.

In a new report summarizing internal control audit problems spotted in 2010 inspections of the eight largest firms, the Public Company Accounting Oversight Board says it counted 46 incidents in 309 engagements, or 15 percent, where auditors failed to adequately support their opinions on internal control over financial reporting (ICFR).

In 39 of those 46 cases, the same firm also failed to adequately support its opinion on the financial statements, the ...