A report from the Natural Resources Defense Council finds "it is virtually certain" oil and gas violations are never reported because of inadequate enforcement.

NRDC published a report Thursday that says not all violations of oil and natural gas safeguards are detected.

"It is virtually certain that some violations are never detected due to inadequate enforcement resources," the report read. "These violations remain unknown to regulators and the public."

Colorado, one of the states with an emerging shale oil and gas sector, had fewer than 40 inspection staff on hand to survey more than 52,000 wells. The state's crude oil production from 2007-13 rose 146 percent thanks in part to the Niobrara shale reserve area, which holds an estimated 2 billion barrels of oil.

Colorado's government in February endorsed recommendations set forth by an oil and gas task force that gave more input to local officials on large-scale drilling operations, though it kept some local control over energy off the table.

The task force was proposed by Gov. John Hickenlooper in November as a way to reach a compromise between communities and the oil and gas industry.

The NRDC finds less than 10 percent of the states with active oil and gas operations have data available on spills or other environmental violations. The report, conducted in coordination with the FracTracker Alliance, finds state governments are skirting their obligations.

"States are falling down on their responsibility to be a watchdog for the people who live there," Amy Mall, a senior policy analyst at NRDC and co-author of the report, said in a statement.

Colorado, however, was one of the three states that post public data about company violations, though NRDC said most of the transparency data it reviewed in those states was opaque or incomplete.

At the federal level, the report found the Department of Interior reported more than 2,000 violations from 1998 to 2011, though there is no public information available after that.