Audit regulators have published the last of the 2013 inspection reports on the eight largest firms, rounding out another blistering year for audit firms as they continue to adjust their audit practices to answer heavy criticism.

The Public Company Accounting Oversight Board published its latest report on Grant Thornton, showing inspectors dug into 36 audit files and found problems with 20 of them, or 55 percent. Inspectors said the deficiencies were significant enough to conclude auditors did not obtain sufficient audit evidence before arriving at their conclusions. In one case, the inspection findings and subsequent work led to a company  restating its financial statements, the PCAOB said.

In 15 of the 20 busted audits, the PCAOB says the firm’s auditors failed to adequately follow standards for the audit of internal control over financial reporting. Inspectors called out seven audits for problems with the auditor’s response to the risk of material misstatement, and five audits with problems in audit evidence.

The PCAOB has called heavy attention to audit problems across all the major firms in audits of internal control and in auditing of revenue recognition and accounting estimates in particular. PCAOB Chairman James Doty warned 2014 inspection reports won’t show significant improvements over disappointing results of 2013 or 2012.

In its response to the inspection attached to the report, Grant Thornton leadership acknowledges 75 percent of the deficient audits show problems with internal control audit work, but also notes the long time lag at the PCAOB between when audits are inspected and when reports are made available. “Since the completion of these audits, which were principally related to calendar year-end 2012 engagements, the firm has implemented a number of significant actions related to auditing internal control as well as other areas and continues to invest resources focused on improving audit quality,” wrote Stephen Chipman, CEO of the firm, and Jeffrey Burgess, national managing partner of audit services.

Across the 2013 audit inspection cycle, Deloitte fared the best with inspectors, with only 28 percent of its audits called deficient, followed by McGladrey at 31 percent, PwC at 32 percent, and Crowe Horwath at 38 percent. Then came KPMG at 46 percent, EY at 49 percent, Grant Thornton at 55 percent, and BDO USA at 65 percent.

The rankings were not dramatically different in 2012, with Deloitte at 25 percent, KPMG at 34 percent, PwC at 39 percent, and McGladrey at 44 percent. The numbers kept getting bigger that year as well, with EY at 48 percent, Crowe Horwath at 50 percent, BDO USA at 55 percent, and Grant Thornton at 65 percent.

Combining the firms’ figures, the average failure rate in 2013 was a bit lower than the year before. The average rate for the eight firms in 2012 was 45 percent, but it inched down to 43 percent in 2013.