Symptoms include include headaches, fatigue, tinnitus and internal bleeding

In this day and age of always-on connectivity, spare a thought for those people who cannot even bear to have any electrical device at all in the same room as themselves.

This is the fate of those who suffer from 'electrical sensitivity', or who believe they suffer from the condition.

The health effects reported by sufferers include headaches, fatigue, tinnitus and skin problems.

But on top of feeling terrible, they are accused of being mistaken, or misled, about the causes of their condition.

Brian Stein, managing director of the £600m chilled food business Samworth Brothers, said: "I am electrically sensitive, a condition which does not exist."

"It is the first time in my life I have not been a credible witness to something. When you are told it doesn't exist and it's psychosomatic it is quite difficult."

Samworth Brothers' customers form a roll-call of the UK's major food retailers. The company's customers include Tesco, Waitrose, Marks & Spencer and Sainsbury's. It owns the Ginsters brand, and is the world's second largest sandwich producer.

Stein was an early adopter of mobile phones in the late 1980s. Seven years ago he started having "weird sensations" and feeling pains in his ear, but kept on using his phones.

"One day I felt a very severe pain, like my eardrum was bursting. I couldn't tolerate putting the mobile phone to my head from then on," he said.

Stein started getting the weird sensations when he came close to a computer, got in his car or watched TV.

He now has an office where he can switch the electricity off. The lights use direct current. There is no PC on his desk, he uses a speakerphone for calls, and his office block has no Wi-Fi.

Stein drives an old diesel car with minimum computer electrical circuitry. At home his bedroom can also be isolated from electricity. He says he sleeps better this way.

"I try and reduce the electromagnetic fields I'm exposed to. If I don't switch the electricity off, after four or five days I know something is wrong. If it was Wi-Fi or computers I'd know after an hour," he said.

"I can't watch television, can't go on electric trains, can't fly long haul. I can't stay in most hotels in London because they've installed Wi-Fi. I can detect it, and in the morning if I go to the toilet I'm bleeding.

"Then, as soon as you go to the doctor and say you're bleeding internally they treat you seriously. If you mention electrical sensitivity, you're mad."

Nobody at Samworth makes a presentation to Stein on a computer, and he laughs that at least one upside to his suffering is that he is spared PowerPoint.

But he will expose himself to technology for client meetings if he thinks its necessary. "What's important to me I'll do. It focuses me," he said.

Stein recognises that his position and wealth mean that he has been able to change his lifestyle and continue with his work and home life.

He has spent £40,000 adapting his home, but he knows people who are not so fortunate and talks of one fellow sufferer sleeping rough in the New Forest to avoid electromagnetic fields.

Stein and his fellow sufferers gather and analyse all the research on electro-sensitivity that is published and get angry about the way some research is carried out, interpreted and ignored.

Some see conspiracies, especially resulting from the UK government's windfall with 3G licences.

In turn this lobby is accused of being selective with the research they cite, ignoring or rubbishing the majority of research which finds that the symptoms of electro-sensitivity are not caused by electromagnetic signals, and misinterpreting other studies.

Stein took part in a study at Essex University investigating whether people who are electro-sensitive could tell whether a phone mast, a source of electromagnetic waves, was switched on or not.

The research found that sufferers couldn't tell. More than 30 studies have found the same thing.

Stein said that he had told the researchers he wouldn't be able to tell at the time whether the mast was on or not, and it would only be later that he would feel any effects.

After his session he says he bled internally for 10 days. He was unable to return to complete his tests, and couldn't contribute to the study's results.

The UK's Health Protection Agency is researching the effects of electromagentic fields but doesn't expect to find evidence that they adversely affect people.

In October the HPA announced a systematic programme of research into wireless local area networks and their use, which will include measurements of exposures from Wi-Fi.

Pat Troop, chief executive of the Health Protection Agency, said: "There is no scientific evidence to date that Wi-Fi and wireless Lans adversely affect the health of the general population.

"We have good scientific reasons to expect the results to be reassuring and we will publish our findings."