Delegates at the Professional Association of Teachers' annual conference in Cheltenham warned that they could be damaging children's health and undermining exam standards.

One telephone company is said to be preparing to market mobile phones for four-year-olds.

In a debate on the issue at the conference, a teacher from Gloucester, Charles Whitney, said mobile phone use had been linked with memory loss and brain tumours.

He urged the government to fund urgent research into the issue.

Cheating

A former head teacher, Hywel Davies, told delegates: "I would simply say ban them from school.

"I'm sure local authorities would support it. And parents who are reasonably minded would back us to the hilt."

A member of the association's council, Geraldine Everett, said using mobile phones could help children develop expertise with information technology.

But she added that children might also use them to cheat in exams.