As the number of deepwater oil and gas wells increased from 256 to 602 over the past decade, surprise inspections of rigs in the Gulf of Mexico dwindled to about three per year, according to an analysis by The Wall Street Journal.

What’s more, not a single surprise inspection of any deepwater gas and oil production platform in the Gulf has been made since 2004, despite a law requiring periodic unannounced inspections. Rigs are the equipment used to drill wells, and platforms are the structures that support the rigs and other equipment. Both rigs and platforms handle vast amounts of oil and natural gas, and are at risk for spills and worker injuries and fatalities.

Overall, the rate of unannounced inspections of deepwater sites dropped from about one in nine in 2000 to about one in 80, according to the Journal’s analysis.

Industry experts say the lack of surprise inspections reduces the likelihood of finding safety violations. Surprise inspections are considered so crucial to ensuring safe mining that Congress is considering a bill that would make it a felony punishable by five years in prison to tip off an operator about an unannounced inspection.

The Minerals Management Service, the agency responsible for overseeing offshore drilling until it was reorganized and renamed after the deadly explosion of BP’s Deepwater Horizon rig, has faced scathing attacks for what critics call a lax enforcement policy (The agency is now the Bureau of Ocean Energy Management, Regulation and Enforcement.).  Federal inspectors spent 62 hours aboard the rig in 2009 in announced visits, and an announced inspection this year about three weeks before the blowout lasted about two hours, but no citation was issued.

Transocean, the company that owned and operated the BP rig, had the lowest rate for surprise inspections among large drilling companies–with surprise inspections accounting for 1 percent of total inspections between 2000 and 2010.

Agency officials say surprise inspections were a low priority in deepwater energy operations, taking a  backseat to mandatory annual inspections of the 3,800 offshore facilities, and to responding to hurricanes and collecting royalties.

Internal investigators have criticized inspectors for being too cozy with oil companies, sometimes even allowing company employees to fill out inspection reports.

An April 2005 memo required a 24-hour notice before inspecting many of the largest offshore platforms, citing new security regulations imposed after the terrorist attacks of 9/11.

The memo’s author, a former regional supervisor for the Minerals Management Service, was fired in 2007, and later pleaded guilty to failing to disclose gifts from an offshore drilling company. The policy of providing notice of inspections was reiterated in 2007 by an employee who subsequently left the agency to work for Chevron Corp.