In the wake of the Gulf oil spill, it seems like every day brings new word of some calamitous failing at the Minerals Management Service, the federal agency charged with regulating offshore oil drilling. There’s an inspector-general’s report citing multiple violations of federal regulations and ethics rules at the agency’s Louisiana office. There’s The Washington Post report detailing how agency officials routinely skirted laws requiring that drilling not threaten the marine environment. There are manifold stories about the cozy relationship between agency “regulators” and the companies they were supposedly watching.

Members of Congress are practically sputtering in outrage, and have seized every opportunity to grill federal officials on how all this could happen. This is understandable and necessary, but one question keeps running through my mind: Where were these members of Congress a few years ago, when intense scrutiny of the minerals agency might have prevented the Gulf disaster?

The same could be said of less-than-robust oversight of the complex financial products that banks were peddling before the financial meltdown, or keeping an eye on the regulators in charge of mine safety, the safety of imported food, or the reliability of corporate credit ratings.

Managing government well is extremely difficult, even for the most accomplished civil servants. Yet far too frequently, we read about mistakes, missteps, actions or the absence of actions by the federal government that disappoint and frustrate us, and they inevitably raise the question: Shouldn’t someone be watching the execution and implementation of these laws?

The answer, of course, is yes: Congress is supposed to be watching. You cannot entirely prevent fraud, financial irregularities, wink-and-nod relationships with regulated industries, conflicts of interest, mismanagement, and efforts by federal officials to sidestep the clear intent of Congress. But certainly we could do a better job were Congress to pursue its oversight role vigorously.

On Capitol Hill, much time and attention go to creating policy. There’s testimony by world-class thinkers, spirited debate, legions of lobbyists, endless negotiation over this or that provision. When you’re dealing with issues of national importance, this is appropriate. However, too many members of Congress — with, thankfully, a few notable exceptions — appear to believe that their job ends when the bill passes. Actually, it should just be beginning.

Whatever action Congress takes on legislation, difficult questions lie ahead in shaping the regulations that follow from it. The federal bureaucrats who craft these regulations often impose their own interpretations on the wording that came out of Congress — and where it is ambiguous, as is often the case, they will in effect interpret the law to suit themselves.

Even if the regulations get written exactly as Congress intended, it’s no guarantee the law will be implemented accordingly — as demonstrated, to take only one example, by reports that the Marine Mammal Protection Act and the National Environmental Policy Act were routinely violated by regulators seeking bonuses for encouraging offshore oil drilling.

As if willful departure from congressional intent weren’t enough, there’s also the plain fact that many pieces of legislation — and certainly all complex ones — have unintended consequences. The Alternative Minimum Tax was passed in 1967 to ensure that a relative handful of wealthy individuals — 155, to be exact — could not continue to sidestep the income tax; today, the AMT affects more than 4 million middle-class taxpayers.

We don’t yet know what unexpected, and probably unfortunate, by-products the recent health-care reform law will produce, but we can be certain that there will be some. Congress needs to be watching carefully.

I am not suggesting that Congress should be involved in the actual management of federal programs. That is the constitutionally mandated job of the Executive Branch. In our system of checks and balances, however, one of the powers that Congress must exercise robustly is to be sure that our laws are being implemented as they were intended to be, and in as fair and just a manner as possible.

Sure, there are federal inspectors-general and a woefully shrinking corps of investigative reporters in the private sector who also see this as their duty, but they have neither Congress’ authority nor its ability to demand fixes and craft new legislation if necessary. If we want to make sure that federal agencies are doing their jobs appropriately, with the best interests of the American people constantly in mind, then Congress must do a better job of oversight, looking into every nook and cranny of their activities.

Lee Hamilton is director of the Center on Congress at Indiana University. He was a member of the U.S. House of Representatives for 34 years.