When Neil Whitfield was diagnosed with a brain tumour at the age of 44, he left the consulting room in shock.

He had been struggling with debilitating headaches, short-term memory loss and fatigue for months, and faced a brutal choice between risky surgery or leaving the tumour where it was and coming to terms with the fact that it would kill him within five years.

But what also shocked him was his doctor’s theory about what had caused the tumour.

“He said he was absolutely convinced it was my mobile-phone use,” said Mr Whitfield, from Wigan, Lancashire. “He told me that mobile phones were going to be the smoking gun of the 21st century in terms of cancers. I hadn’t even thought about it before.”

At the time of his diagnosis in 2001, Mr Whitfield was working as a sales manager and had been a regular user of mobile phones since 1995. He never used one again.

After surgery, he was left deaf in one ear and suffered some facial paralysis, but has been given the all-clear. His employers, however, did not see eye to eye with his decision not to use a mobile. “I basically got ‘managed out’,” he says. “When I went back to work and explained that the tumour had been near my ear, they said, ‘Well, can’t you just put the phone to your other ear?’ It was ludicrous.

“I now run my own training agency without a mobile – it can be done, but we have all become so reliant on mobiles that we think we can’t survive without them.”

His sons, aged 13 and nine, do not own mobiles and are not too bothered about their father’s ban. “If people ask, they just explain what happened to me,” says Mr Whitfield. “So many people don’t know about the risks. If mobile phones were a food, they would have been taken off the shelves by now.

“I don’t know any parent who would hand their child drugs and say, off you go, yet virtually every kid has a mobile. I find it terrifying.”

But just what the risks are for children is still open to fierce debate. Last week, the Department of Health announced that it had commissioned the world’s largest study of the effects of mobile-phone use. The two-year Study of Cognition, Adolescents and Mobile Phones (Scamp) will look at 2,500 children aged 11 and 12. They will be asked about phone use and tested on functions such as memory and attention to see whether the use of mobiles has any impact. It has been suggested that children and teenagers could be more vulnerable to radio-frequency exposure because their nervous systems are still developing.

Around 70 per cent of 11- and 12-year-olds in the UK now own a phone, rising to 90 per cent of children over 14. One recent phone app even encourages parents to download nursery rhymes and place the device on a child’s pillow so they can be soothed to sleep with lullabies. And although the 2005 Stewart report on phone technology recommended that children under 16 should only use mobiles for essential calls, the reality is that most teenagers spend hours on them a week.

So what are the risks? Experts may not agree on whether phones cause cancer, but there is a consensus that excessive use is leading to a rise in other related issues, such as repetitive strain injury (known as “texting thumb” by some doctors) and attention problems in some children.

And although most studies have not found any firm link between mobile-phone use and cancers or other health problems in children and adults, pressure groups and some scientists dispute those findings. Denis Henshaw, Emeritus Professor at Bristol University and honorary scientific director of the Children with Cancer UK charity, is one of them.

“The dangers are being seriously underplayed,” he says. “We are seeing a rise in brain tumours in adults and children. And because brain tumours are relatively rare, we are talking small numbers, but the increase is there.

“Why should it come as any surprise that holding the equivalent of a small microwave oven to your ear should be a health risk?”

Prof Henshaw and others believe that mobile phone packaging should carry cigarette-style public health warnings rather than the advice being buried in manufacturers’ manuals. And Mr Whitfield agrees. “After I was diagnosed, I looked at my phone manual and very, very far down it says you should keep your phone at least 10mm away from your body at all times,” he says. “Hardly anyone reads those manuals, but even the manufacturers are admitting there is a safety issue here.”

Prof Henshaw also believes the growth in mobile-phone use over the past decade means that most scientific studies have yet to record the real effects on health.

But Prof Anthony Swerdlow, of the Institute of Cancer Research, disputes the claim that there has been an increase in brain tumours in children, saying Office for National Statistics figures show only a small increase in much older people. “We can’t be sure, but there is no evidence to show there is a link with brain cancers.”

The biggest study to date also failed to resolve the issue. The Interphone study, published in 2010, studied 13,000 adult users in 13 countries over 10 years. Researchers found that heavy users had a slightly higher risk of gliomas (a type of brain tumour), but concluded that they had neither proved a link with brain cancers, nor demonstrated that there wasn’t a risk.

Other scientists are not so sure. A Swedish researcher, Prof Lennart Hardell, has published a controversial paper that found children who use mobiles are five times more likely to develop brain tumours, although his results have been questioned by many scientists.

A French study, published last week, also found that heavy users of mobile phones may be at higher risk of gliomas and meningiomas. Researchers from the University of Bordeaux compared 447 adults with the tumours with a control group of almost 1,000 healthy people. They found that people who used their phones for more than 15 hours a month over five years were up to three times more likely to develop the tumours compared with those who rarely used a mobile.

But even the researchers admitted that the findings did not take into account other factors, such as smoking.

Phones and how we use them have also changed in the past 10 years. Most teenagers are now more likely to be texting and messaging than holding a device to their ear, and new smartphones emit fewer radio waves.

In 2011, the World Health Organisation’s International Agency for Research on Cancer classified mobiles as a “possible carcinogen”. But the decision was highly controversial – some members of the scientific committee walked out of the proceedings in protest.

But certain countries are taking action. France has banned mobiles and Wi-Fi in primary schools, while phone shops in Canada are required to hand out safety leaflets.

Last year, the Italian supreme court ruled that a businessman’s brain tumour had been caused by mobile-phone use, in a case that could pave the way for European-wide class actions. The case has yet to be resolved.

But the mobile phone industry remains buoyant. “A large number of studies have been performed over the last two decades to assess whether mobile phones are a potential health risk,” says John Cooke, executive director of the Mobile Operators Association. “To date, no adverse health effects have been established.”

For parents, the health risks are important – but a straw poll of mothers on Facebook last week found that many are more concerned about another impact of phones on their children.

“My son and his friends are messaging on their phones all the time,” said Hayley Brown, mother of a 17-year-old son and eight-year-old daughter. “I do worry about the health risks but I’m also concerned that they are losing the art of normal social interaction. It seems to be the only way they can communicate now.”