Doctors are calling for the ban on mobile phones in hospitals to be at least partially lifted, saying the evidence that they might cause serious harm by interfering with vital equipment is "flimsy".

Patients and staff already flout the rules, with medical teams even leaving phones switched on in operating theatres, according to reports in two medical journals.

Bans were introduced in the early 1990s after a warning from the government's medical devices agency about potential hazards, but more "sensible and considered" restrictions on mobiles should now be used, say doctors.

In a letter to the Lancet, doctors at St Mary's hospital and Imperial College, London, argue that "the absence of any real evidence of risk to patients' safety, coupled with advances in hand held technology, should cause hospital trusts and their advisory bodies to reappraise restriction".

Phones have become an "essential communications tool", and bans are hard to enforce. "The reality is that mobile phones are used in hospitals by patients, their relatives and medical staff. At present, even when on hospital premises, many consultants prefer to be contacted by mobile phones," they write. "Some hospitals have issued specialist registrars with mobiles so they can be contacted directly [by GPs] ... In our experience mobiles are frequently left on in operating theatres, where such potentially vulnerable equipment is in use."

Doctors at the John Radcliffe hospital, in Oxford, have also questioned the bans, saying any interference is temporary and localised. They praised the "enlightened approach" of the Chelsea and Westminster hospital, in London, where restricted use is permitted.