Manchester Airport has been forced to rethink trials of its invasive new X-ray machine after claims the "naked" images of airline passengers could violate child pornography laws.

This week, the airport began a year-long trial of the full-body scanner, which can instantly detect any hidden weapons or explosives without passengers having to remove any of their clothing - such as shoes and belts - for a search.

A combination of images shows an airport staff member demonstrating a full body scan at Manchester Airport. Credit:AFP

It effectively does away with the need to frisk passengers and is expected to speed up the security process at airports, but the cost of that is passengers are starkly naked in front of security staff. Genital outlines are clearly visible on the screen.

The scanner's manufacturer, RapiScan, is already eyeing further airports around the world. A few weeks ago it sold 30 of the $US160,000 ($174,000) scanners to the US Transportation Security Administration, Forbes reported.