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.
Private prosecution
Mr Coghill, who runs an independent laboratory in Pontpool, Gwent, is bringing a private prosecution against a telephone shop where he bought two phones.
Mr Coghill is convinced that mobile phones pose a major health hazard when used for more than 20 minutes at a time.
He says the mobile phone is the biggest domestic appliance source of radiation ever invented.
Mr Coghill has produced evidence that suggests that radiation from mobile phones can cause headaches, memory loss and severe damage to the immune system.
He is on record as saying: "Anyone who uses a mobile phone for more than 20 minutes at a time needs their head examined."
The court later heard from Dr Christopher Busby, the UK representative on the European Committee on Radiation Risk.
Dr Busby compared the energy generated in the brain when using a mobile phone to "a light bulb being switched on".
He said: "I am not surprised when people say they are getting headaches when they use mobile phones if we are talking about these levels of density."
Dr Busby was concerned that the risk of using mobile phones was not recognised by authorities such as the National Radiological Protection Board.
Echoes of the BSE crisis
He compared the delay in recognising the risk to the early days of the BSE crisis when scientists said the disease could not cross the species barrier.
"There is quite a considerable time lag involved before these conservative bodies like the National Radiological Protection Board say `okay we can see there is a risk now'," Dr Busby told the hearing.
"But because there is a lag between exposure to cancer causing agents and the manifestation of cancer this time lag results in the death of a lot of people."
Barrister Hugo Charlton, who has been hired by Mr Coghill to fight his case, said: "Legislation says that goods should carry instructions or warnings.
"But at the moment the shop is doing nothing to warn the public about any risks.
"We say that a warning against excessive use would be reasonable in making the product safer."
Experts from the government's National Radiological Protection Board are due to give evidence supporting the shop.
A spokesman said: "There is no firm evidence of any serious health effects from using mobile phones."
Magistrates at Abergavenny are due to spend two days hearing the case