The equality watchdog has called on the government to explain its plans for the use of body scanners at airports, citing concerns about racial profiling and privacy.
This weekend the Equality and Human Rights Commission said it had written to the Home Secretary Alan Johnson to urge the "utmost caution" over such technology.
Backscatter X-ray body scanners, which produce a ghostly naked image of their subjects, are currently in trials at Manchester Airport. The UK's largest airport operator, BAA, has said it will install machines "as soon as is practical" at Heathrow.
"The Commission is concerned that that the proposals to introduce body scanners are likely to have a negative impact on individuals' rights to privacy, especially members of particular groups including disabled people, older people, children, transgendered people, women and religious groups," it said.
"Under the Human Rights Act, any infringement of the right to privacy must be justified, necessary and proportionate."
The Commission was set up to independently monitor Human Rights Act compliance.
In the wake of Umar Farouk Abdulmutallab's failed Christmas Day bombing of a transatlantic airliner above Detroit, Gordon Brown said the government would "examine a range of new techniques to enhance airport security systems... these could include advancing our use of explosive trace technology, full body scanners and advanced x-ray technology."
Johnson has also suggested that air travellers could be selected for scanning by "additional targeted passenger profiling".
"We will be considering all the issues involved, mindful of civil liberties concerns, aware that identity based profiling has its limitations, but conscious of our overriding obligations to protect peoples' life and liberty," he told the Commons earlier this month.
The Commission yesterday warned Johnson that discrimination on racial or religious grounds is illegal.
"In the absence of any evidence provided by the government, the Commission remains to be convinced that the proposals on profiling set out by the Home Secretary are an effective response to the current threat, and are therefore justifiable," it said.
"The Commission is therefore not convinced that the proposals amount to a lawful, or proportionate response to the current threat."
Body scanners have also drawn fire from child protection groups. The Manchester trial also had to be revised last year after suggestions that scanning children could violate child pornography laws. ®