(CNN) Complaints filed against senior military officials have increased over the past few years, but fewer cases are being investigated and even fewer senior officers are found guilty of misconduct, according to data from the Defense Department inspector general.

"Only a very small percentage of these officials fail to uphold the high ideals and ethics required of their critical positions," Glenn Fine, the inspector general, told lawmakers Wednesday. "However, some do commit misconduct, either willfully or negligently. When they do, they need to be held accountable."

During fiscal year 2017, the most recent year for which data was released, there were 803 complaints filed compared with 787 in the prior year, according to information released Wednesday during a House Armed Services Military Personnel Subcommittee hearing. However, of those 803 complaints, only 144 were investigated by the Inspector general. Of those 144 cases, there were just 49 substantiated senior misconduct cases. That's down from a high of 85 substantiated misconduct cases against senior leaders in 2012.

In written testimony provided to the House subcommittee, the Department of Defense's inspector general said that in fiscal year 2017, the number of cases "involving substantiated senior official misconduct involved approximately 2 percent of the DoD senior official population."

Fine said the time to finish investigations had more than doubled between 2015 and 2017, from 235 days to 472 days.

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