Washington (CNN) -- More than 30 privacy and civil liberties groups are asking the Department of Homeland Security to suspend the use of full body imagers at airports, saying there is evidence that privacy safeguards don't work and the devices are not effective.
In a petition filed Wednesday, the groups also said the machines -- which see through travelers' clothes -- violate people's "deeply held religious beliefs."
The Transportation Security Administration has sped up deployment of the machines after a man with explosives sewn into his underwear attempted to bomb a plane on Christmas Day. About 46 machines are in place in 23 airports, and the agency plans to have about 1,000 set up by the end of 2011.
The TSA has steadfastly defended the effectiveness and safety of the machines and says extensive precautions are taken to protect the identities of those who go through them.
But in a petition released Wednesday, the coalition of groups said the machines are "uniquely intrusive" and violate travelers' Fourth Amendment rights against unreasonable search.
"At this point, there is no question that the body scanner program should be shut down," Marc Rotenberg, president of the Electronic Privacy Information Center, said in a prepared statement. "This is the worst type of government boondoggle -- expensive, ineffective and offensive to Constitutional rights and deeply held religious beliefs."
Security expert Bruce Schneier called the machines "one more example of security theater."
The head of the Asian American Legal Defense and Education Fund said the use of the machines "has violated and will continue to violate the civil rights of Muslims and other religious groups."
Rotenberg said the groups may seek legal action if the DHS does not act on the petition.
Rotenberg and TSA has tussled over the issue of whether the imagers can retain images. In a February 24 letter to the chairman of the House Homeland Security Committee, TSA said the machines "have the capability to retain and export images only for testing, training and evaluation purposes."
"Machines are delivered to airports without the capability to store, print or transmit images, and cannot be modified by the operators," it said.
"There are no circumstances when the system would be entered into the test mode in an airport environment," TSA's acting administrator Gale Rossides wrote in the letter.
Rotenberg said the use of the word "would" instead of "could" is intended to conceal the true capabilities of the machines. The machines can be altered at any site to retain and export images, he said.
In recent weeks, the TSA has publicized the machines' effectiveness in detecting contraband. In the first year of deployment, the machines found about 60 "artfully concealed" illegal or prohibited items, TSA said.
While no explosives have been detected, the machine's ability to spot even small concealed objects demonstrates its effectiveness as a security tool, officials said.
"It is absolutely a tremendous improvement of what we can detect at the checkpoints," Rossides told CNN earlier this month. "It is an excellent piece of technology that will significantly improve our detection capabilities."
Screeners using the technology have found concealed drugs, a knife secreted in the small of a person's back at a Richmond, Virginia, airport, a concealed razor blade on a passenger at a Phoenix, Arizona, airport and other concealed items such as large bottles of lotion, which are prohibited as carry-on items.
In addition, the machines have revealed numerous prohibited items that passengers evidently inadvertently left in pockets. Those items are confiscated but are not counted in the tally, a TSA spokesman said.
"The amazing thing is that our officers, as they get more and more familiar with this technology, are actually finding very, very small things that are being secreted on the body," Rossides said.
The organizations signing the petition include EPIC, AALDEF, BORDC, the Council on Islamic-American Relations, the Center for the Study of Responsive Law, the Liberty Coalition and Public Citizen.