An electronics expert has claimed that some people who use mobile phones heavily have started to develop cancer.
Researcher Alisdair Phillips made the claim during a legal hearing brought by scientist Roger Coghill, who is trying to force retailers to put health warnings on mobile phones.
Mr Phillips told the court: "I have received frequent reports from regular phone users telling of headaches, loss of concentration, skin tingling or burning and twitching.
"The complaints can involve eye tics, short-term memory, buzzing in the head at night and other effects such as tiredness.
"This is the first time in human existence that people have wandered around with radiating devices held close to their bodies.
"We have got numbers of people that are now unable to work who have been using mobile phones up to seven or eight hours a day.
"A lot of people coming to me have been heavy users. All have been City traders and British Telecom employees who are expected to use their phones every day.
"It is too early to say, but we are starting to see lymphomas of the neck in heavy phone users."
Mr Philips told the court: "If someone is completely healthy and has a strong immune system then mobile-phone use may well not give them long-term health problems.
"Some people can smoke for forty or fifty years and not develop cancer and yet the dangers of smoking are now generally accepted.
"It has been repeatedly shown that a few minutes exposure to cell phone type radiation can transform a 5% active cancer into a 95% active cancer for the duration of the exposure and for a short time afterwards."
Mr Phillips, a consultant advisor on electromagnetic fields, led a team of investigators examining possible health dangers in the Kuwait telephone system.
He said: "I believe there is now adequate evidence to insist that all mobile phone handsets should be required to have a suitable warning label."
He said the warning label would meet the requirements of the Consumer Protection Act.