A new X-ray machine at London's Heathrow Airport, which sees through passengers' clothes, has been attacked by civil liberties campaigners as a "voyeur's charter".
The machine uses low-level radiation to see through clothing, producing an anatomically detailed black and white image of the body underneath.
Capable of detecting solid objects concealed under clothing, it started a four month trial in October.
Randomly picked passengers are asked if they will volunteer to be scanned by the machine.
"I stood in front of the screen and they took three pictures in different positions," said passenger Pernille Nielsen. "I don't mind if the pictures are a little more personal as long as I'm safe in air -- that's what matters," she said.
Another passenger, Maria Love, said: "It's all about being safe, and I really have no problem with it."
A spokeswoman for BAA Heathrow said 98 percent of participants gave positive feedback.
But British civil rights group Liberty called the X-ray images unjustified and intrusive. "We obviously do not object to taking security measures, but I remain totally unconvinced that it is necessary," a spokesman said.
To justify the intrusion, the airport should show current detectors are inadequate, he added. "It's an obvious invasion of people's privacy -- it's a voyeur's charter."
The American Transport Security Administration, which has considered using the machines at US airports, echoed Liberty's concerns. "There are a number of privacy issues that need to be addressed before we would do field tests," a spokeswoman said.
Scanners currently looking for concealed weapons or explosives on passengers have shown limitations in the past.
Traditional X-ray machines used to scan baggage have often struggled to identify plastic explosives, accidentally sounding alarms when detecting chocolate, cheese and peanut butter because of their similar density to the explosive Semtex.
Heathrow, which for security reasons declined to say how the new X-ray machine improves on current scanners, denies the machines could cause embarrassment.
"It's a very low dose X-ray, the images are not stored, it's same sex operated and the operator that sees the image will not see the person," said the airport spokeswoman. "There will not be a situation that could cause embarrassment," she added.
Heathrow is one of the world's busiest airports, handling around 64 million passengers a year.
