The oil that's creeping toward the Gulf of Mexico shoreline might also be threatening your portfolio. If you own shares of an oil company, beware: The contamination goes way beyond BP (NYSE: BP). James Early, lead advisor of Motley Fool Income Investor, believes that any oil and gas company drilling in the Gulf of Mexico should be girding for a sea change in its operations, and investors should take heed.

Part of the reason for this is the expense of the massive spill -- legal and environmental costs that will be on the books long after the oil itself has dissipated. But another reason is regulation. Remember The Wall Street Journal's 2008 expose on Mineral Management Service, the government agency that was partying while it was supposed to be monitoring the safety of oil company activities in the Gulf? Well, the MMS was also on duty when BP sprung a leak last month. As sure as oil and water don't mix, the agency will be forced to step up its oversight, which means that oil derricks in the Gulf will be put through the bureaucratic paces -- and slowly.

James Early says investors would do well to avoid oil producers with significant exposure in the Gulf of Mexico -- not just BP, but also Apache (NYSE: APA) and Anadarko Petroleum (NYSE: APC) -- and consider foreign firms such as Brazil's Petrobras (NYSE: PBR) or France's Total (NYSE: TOT), which are better diversified around the globe. Watch the video here: