The audit comes after a Times investigation last year revealed that the department had routinely misclassified serious assaults as minor offenses that weren't counted in the city's crime rate.
The new review examined one crime category: aggravated assault. Based on sampling done by auditors, officials estimate that there were actually 23% more aggravated assaults in 2014 than the LAPD originally reported.
The LAPD's original crime statistics showed serious assaults jumped 28% last year. But the audit suggests that the increase was even higher.
Auditors concluded that the "department did well with classifying crime."
But Los Angeles Police Commissioner Robert Saltzman questioned that conclusion.
"If, in fact, the error rate is 20%, that does not strike me as doing well," Saltzman said.
The LAPD acknowledged that the audit itself understated the impact of the error rate by saying serious assaults would have been 19% higher had they been reported correctly. LAPD Inspector General Alex Bustamante calculated the correct figure was 23%, Assistant Chief Michel Moore told police commissioners Tuesday.
The Times investigation was based on crime numbers from a one-year period ending in September 2013. Following the report, the LAPD instituted a series of reforms including additional training, new accountability rules and the establishment of a Data Integrity Unit to ensure accuracy in crime statistics sent to the FBI.
LAPD officials stressed that the new audit was conducted before the reforms and training took effect this year and said future error rates should improve.
"I am confident that the systems we put in place will make us much better," Chief Charlie Beck said at a news conference.
Saltzman said he was pleased with the progress the LAPD has made to address reporting errors after the department was initially "pretty defensive" about the problems last year.
The Police Commission instructed Bustamante last year to conduct an audit into the department's crime statistics. That report is expected to be released this fall, officials said.
The latest audit analyzed a random sample of about 1,000 serious and minor assaults. The error rate identified for minor assaults was higher than those in two previous audits in 2012 and 2011.
The highest misclassification rate was found in the LAPD's Central Bureau — which includes downtown, northeast and east L.A. — where 13% of minor assaults were incorrectly categorized.
Moore said the department's goal is to hit 100% accuracy on its statistics, but acknowledged that is a tall task at an agency that handles more than 100,000 serious crimes a year.
The LAPD's antiquated records management system presents a major hurdle in improving accuracy and officials would like to see it replaced, Moore said.
The audit, which looked at both the underreporting and over-reporting of serious assaults, has a margin of error of plus or minus 2%.
Jay Wachtel, a criminal justice professor at Cal State Fullerton, said the audit findings indicate that fives times as many mistakes were made in underreporting serious attacks compared with over-reporting minor assaults.
"The direction of the error is in the old, bad direction," Wachtel said. "It tells me it's not about the numbers, it's about the inside organizational pressures that persist because the measure of success is still bringing down crime."