STRASBOURG, France (AP) -- EU lawmakers have joined U.S. civil liberty campaigners in criticizing a new scanner that allows airport security to see through passengers' clothes, calling it a virtual strip search that should only be used as a last resort.

The new system, which the European Union plans to authorize at the bloc's airports, allows guards to see an outline of passengers' bodies beneath their clothes, making it easier to detect any concealed objects.

It already is being introduced in several U.S. airports and has been tested in other countries around the world, including EU nations such as Britain and the Netherlands.

However, EU officials said it could face a ban if the 27-nation bloc does not include it in a new regulation listing acceptable airport security equipment.

"Many travelers will consider these scanners an enormous intrusion" on their personal privacy, Philip Bradbourn, a British Conservative member of the EU assembly, said Tuesday.

Bradbourn said the technology should not be used routinely on passengers, but could be introduced when suspicions are raised.

"There may be some benefit in having body scanners in our airports, but they should be a last resort and a substitution for a strip search, not a random sample of innocent holiday-makers," he said.

The plans have provoked concern from across the political spectrum, and many EU lawmakers issued statements ahead of Tuesday night's debate about the matter in the European Parliament, which is based in the eastern French city of Strasbourg.

The EU's executive body, the European Commission, says the legislation under consideration would respect safety and privacy rules, adding that passengers who objected could be offered an alternative form of security check.

The American Civil Liberties Union has long campaigned against use of the scanners for routine checking at U.S. airports, saying they should only be used in place of an intrusive search when there is probable cause.

After the machines were introduced at Amsterdam's Schiphol airport last year, officials there said they had few complaints from passengers, saying most approved because lines moved faster.