ON AT least 22 occasions between July 2011 and September 2012, a D.C. employee improperly used a Maryland disabled parking placard to park his car for free at the Department of Consumer and Regulatory Affairs. The District’s Inspector General’s Office recommended that the employee in question be sanctioned. But what might seem a routine, even trivial, matter has become anything but.

In response to the inspector general’s report, the District’s ethics board scheduled a normal hearing on the sanctions to be given to the employee. But the ethics board almost couldn’t proceed because, in an increasingly hostile internecine struggle, the Inspector General’s Office initially refused to disclose certain relevant documents for the case.

“We can’t just let someone look at our entire files,” the current inspector, Charles J. Willoughby, told The Post’s Mike DeBonis last week. “We have to determine what is relevant and appropriate.”

In response, the ethics board threatened to fire back with a subpoena. Luckily, it didn’t have to resort to pursuing one because the documents were handed over. While this specific squabble may have been resolved, the larger issue still stands. Two sister government agencies nearly went to war over the question of oversight.

There’s no reason these two agencies shouldn’t be able to work in tandem. The Inspector General’s Office has a much larger budget — nearly $16 million annually — not to mention a team of investigators to deploy on the cases it explores. By contrast, the ethics board, which began operations only last October, has the power to levy sanctions but runs on roughly $1 million per year and, thus, relies on the information the IG’s office provides.

One would assume that the former could use its considerable resources to investigate appropriate cases and that the latter could then pursue those cases after the information was gathered. But that, along with many sensible propositions in D.C. politics, would be wishful thinking.

During its investigation of Jim Graham (D-Ward 1) last fall, the ethics board second-guessed some of Mr. Willoughby’s conclusions. Now the inspector general risks creating the appearance of being more interested in guarding his own territory than promoting accountability. Nowhere in these proceedings was his office’s independence at risk.

Council member Kenyan McDuffie (D-Ward 5), chairman of the committee that supervises both agencies, has introduced legislation that would expand the ethics board’s rights to review records from other D.C. agencies, including those of the inspector general. That’s a fine idea, one that would give the board the authority it needs to do its job.