The equality watchdog has written to the home secretary to express its concern that airport body scanners risk breaching an individual's right to privacy.

The Equality and Human Rights Commission is calling on the government to set out its justification for the scanners, which Gordon Brown has said will be gradually introduced at British airports following the attempt to blow up a plane over the US on Christmas Day. The EHRC says the proposals are likely to have a negative impact on privacy, especially for disabled people, elderly people, children and transgender people.

The commission has written to the home secretary, Alan Johnson, to clarify what safeguards will be put in place to protect passengers.

It also wants to see the evidence for the profiling of travellers in the context of selecting people to be scanned. Equal rights campaigners have aired concerns that the process will lead to discrimination against people on the grounds of race, ethnicity of religion.

John Wadham, group director legal at the EHRC, said: "The commission fully accepts the government's responsibility to protect the safety and security of air travellers. The right to life is the ultimate human right and we support the government reviewing security in the light of recent alleged terrorist activity.

"However, the government needs to ensure that measures to protect this right also take into account the need to be proportionate in its counter-terrorism proposals and ensure that they are justified by evidence and effectiveness."