If anyone wonders why Americans distrust Congress, they need only consider recent findings of the House ethics committee — supposedly, the cop on the beat — that enable an atmosphere of corruption.

In fact, evidence in one case strongly suggests that the committee’s former chairwoman, the late Rep. Stephanie Tubbs Jones (D-Ohio), colluded in allowing Members to violate House rules.

In another case, exonerating all seven Members investigated for ties to the now-defunct lobbying firm PMA Group, the ethics committee acknowledged that campaign contributors often think they are buying the earmarks they get from Members — and that Members know it — but recommended nothing to alter the situation.

The committee “admonished” House Ways and Means Chairman Charlie Rangel (D-N.Y.) and Jones’ former committee counsel in connection with two Caribbean trips paid for by several corporations, in violation of House gift rules.

But House rules, unlike the Senate’s, do not recognize “admonishment” as a sanction. So we interpret the wrist slap here as even weaker than a “reproval,” the House’s lowest level of punishment.

The panel also forced Rangel and five other Members to repay the cost of the trips. But the five were exonerated of wrongdoing on the grounds that they did not know of the sponsorship. Rangel was admonished because staffers knew.

All this presumes that people smart enough to get elected to Congress can’t put two and two together when representatives of Pfizer, American Airlines and IBM, among other firms, show up as “sponsors” of their junkets to Antigua and St. Maartens.

But, they can say — as Rangel did — that the trips were approved by the ethics committee. According to the committee, Jones’ former counsel, Dawn Kelley Mobley, colluded with the ostensible sponsor of the trips, the Carib News Foundation, in concealing corporate payments.

And in a report of the Office of Congressional Ethics, Rangel’s former chief of staff is quoted as saying that Mobley was acting on orders of Jones herself and that “we celebrated” when Jones was appointed by Speaker Nancy Pelosi (D-Calif.) to chair the ethics committee because she would find a way to allow the trips to proceed.

Jones died in August 2008 and can’t defend herself. But the whole episode taints the House.

And so does the committee’s unanimous exoneration of the late Rep. John Murtha (D-Pa.) and six others in the PMA affair.

The committee said its investigation “did find that there is a widespread perception among corporations and lobbyists that campaign contributions provide enhanced access to Members or a greater chance of obtaining earmarks.

The report stated that “Members, by and large, take great care to separate their official and campaign functions,” usually by having separate aides handle those duties. But the committee also had evidence that Murtha, at least, knew full well that his campaign donors thought they were improving their chances of getting earmarks and that he dealt directly with PMA’s top lobbyist.

The ethics committee could not prove any quid pro quos, but the public doesn’t believe for a minute that lobbyists expect nothing for the millions they bestow on Members. It’s part of the reason Congress has an 18 percent approval rating.