CONGRESS HAS BECOME a habitual loser in public-opinion polls, and the latest installment in The Post’s series on the congressional ethics system helps to show why.

The Post found that lawmakers can and do sponsor legislation that could benefit business interests in which they or their families have a stake. Examples include former Rep. Dennis Cardoza (D-Calif.), a racehorse owner who co-sponsored a bill to lower taxes on racetrack purses, and Sen. Jeff Sessions (R-Ala.), who has a large stake in timber and pushed for tax reforms relating to the industry.

These sorts of activities are legal, and many members of Congress offer plausible explanations for why their actions shouldn’t concern voters. But The Post’s findings should not make anyone comfortable.

Nor should other odd facts The Post has detailed about congressional ethics rules. Lawmakers can trade in firms lobbying on legislation in their committees. They can steer money to projects that favor their family’s finances, as long as they aren’t the only ones who benefit. House members don’t have to disclose when they direct cash to organizations associated with their children or other relatives or when they fund projects that would make their land holdings more valuable.

No congressional ethics regime can prevent every conflict of interest, nor should lawmakers try to design one that would. At some point, Congress would inappropriately cordon off members from issues they know about.

Yet there is ample room for improvement in the rules. Many members of Congress say that they consult with the congressional ethics committees before taking questionable actions. More of the committees’ advice should be available to the public, particularly when legislators claim to have a committee’s blessing. Lawmakers should examine the requirements they have set for officials in other branches, such as divestment from personal holdings in certain industries or recusal among judges. Legislators could lessen suspicions by putting their assets into blind trusts.

The best thing would be to beef up the Office of Congressional Ethics. Created in 2008, this independent body can investigate at will and refer its preliminary findings to the House or Senate ethics committee. Though the lawmakers on the committees are Congress’s final ethical arbiters, they must comment publicly on every case the ethics office refers to them. Not surprisingly, legislators have tried at times to gut the ethics office. They should go in the opposite direction, ensuring steady funding and granting the office subpoena power. That might not save Congress’s reputation, but it would be the right thing to do.