PITTSBURGH — Pennsylvania regulators aren’t inspecting tens of thousands of oil and gas wells even once a year, a new report says. But state officials say they’re inspecting most new wells in the Marcellus Shale region, which is the right place to focus.

The report issued Tuesday by Earthworks, a Washington, D.C., nonprofit, found that more than 66,000 active wells weren’t inspected by the Department of Environmental Protection last year, and that many companies cited for violations aren’t punished.

DEP spokesman Katherine Gresh said in a statement that the agency inspected 78 percent of newer shale gas wells last year, and that older conventional wells usually operate for decades without problems. She said that failing to note the major differences between old and new wells “is comparing apples to oranges and misleading the public.”

Earthworks says the number of inspections doesn’t meet the goal of DEP’s own guidelines, even for new wells.

“There’s at least a quarter of all new wells that aren’t getting inspected. We still think that’s not good enough,” said Bruce Baizel, an Earthworks staff attorney.