The body scanners coming to your local airport provide marginal benefits — if any — in detecting weapons and explosives hidden on travelers. They aren’t worth the cost in money — let alone in civil liberties.

The Transportation Security Administration has put these machines — X‑ray and radio-wave booths that look beneath clothing to perform virtual strip searches — across the nation and around the world. Industry advocates claim the technology’s needed to stop terrorists with explosives hidden under their clothes like Christmas bomber Farouk Abdulmutallab.

Yet the public is justifiably skeptical. Pilots and passengers are “opting out” and taking the alternative screening method — a run through a traditional metal detector and an all-too-intimate pat-down. Cell-phone videos of encounters with TSA screeners are going viral.

Air travelers now face a few bad choices: Submit to the body scanner, endure an invasive manual pat-down or accept an $11,000 civil fine. This is security theater at its finest. Congress needs to revisit these protocols completely — starting with a total halt to the obscenely expensive and jarringly ineffective full-body scanner.

Despite what their proponents would have us believe, body scanners are not some magical tool to find all weapons and explosives that can be hidden on the human body. Yes, the scanners work against high-density objects such as guns and knives — but so do traditional magnetometers.

And the scanners fare poorly against low-density materials such as thin plastics, gels and liquids. Care to guess what Abdulmutallab’s bomb was made of? The Government Accountability Office reported in March that it’s not clear that a scanner would’ve detected that device.

Even if the scanners did work against low-density materials, the same group linked to the Christmas bomb, Al Qaeda in the Arabian Peninsula, has already found another way to defeat the technology: hiding bombs inside the human body: A would-be AQAP assassin tried to kill a senior Saudi counterterrorism official with a bomb hidden where only a proctologist would find it.

That bomb wound up killing only its carrier. But a more enterprising terrorist could go to the plane bathroom to remove bomb components hidden in a body cavity, then place them against the aircraft hull — and the results would be far different.

Terrorists already know how to beat body scanners with low-tech (really, no-tech) techniques, but the federal government still spends billions on this gadget.

If the ineffectiveness of body scanners is not enough to give the public pause, the cost ought to be.

An army of executives for scanner-producing corporations — mostly former high-ranking Homeland Security officials — successfully lobbied Congress into spending $300 million in stimulus money to buy the scanners. But running them will cost another $340 million each year. Operating them means 5,000 added TSA personnel, growing the screener workforce by 10 percent. This, when the federal debt commission is saying that we must cut federal employment rolls, including some FBI agents, just to keep spending sustainable.

Why cut funding for the people who actually catch terrorists to add more pointless hassles at the airport? (Going through a body scanner also takes longer — the process is slower than magnetometers.)

Scanners clearly fail an honest cost-benefit analysis. Yet it’s privacy that has the traveling public up in arms. Understandably so — the message the TSA is sending us is: “Be seen naked or get groped.”

We tell our children not to talk to strangers, but now a government functionary gets to fondle away just because he has a badge?

Thanks, but no. Policymakers should rethink this move toward ineffective, expensive and unnecessarily intrusive aviation security.