Britain's children are being poisoned by a "junk culture" of processed food, computer games and over-competitive education, an influential group of authors and experts warned on Tuesday.
In an open letter to the Daily Telegraph, 110 teachers, psychologists and children's authors - including the internationally acclaimed Philip Pullman and Penelope Leach, a leading childcare expert - called on the government to act now to prevent childhood being killed off altogether.
Forced "to act and dress like mini-adults", children are becoming increasingly depressed and experiencing growing levels of behavioural and developmental problems, they said.
"Since children's brains are still developing, they cannot adjust as full-grown adults can, to the effects of ever more rapid technological and cultural change," the letter said.
"They need what developing human beings have always needed, including real food (as opposed to processed "junk"), real play (as opposed to sedentary, screen-based entertainment), first hand experience of the world they live in and regular interaction with the real-life significant adults in their lives."
The letter was circulated by Sue Palmer, an ex-head teacher and author of a book entitled "Toxic Childhood", and Dr Richard House, a senior lecturer at the Research Centre for Therapeutic Education at Roehampton University in London.
"Children's development is being drastically affected by the kind of world they are brought up in," Palmer told the Daily Telegraph. "It is shocking."
"A child's physical and psychological growth cannot be accelerated. It changes in biological time, not at electrical speed. Childhood is not a race."
The experts condemned Britain's increasingly "target-driven" education system and urged the government to recognise children's need for more time and space to develop, demanding an urgent public debate on child-rearing in the 21st century.
Award-winning children's author Michael Morpurgo, who also signed the letter, said there was a "drip, drip, drip effect" of academic pressure and marketing which was killing childhood.
"It's gradually soaking like a poison into the culture," he told BBC radio. "There is less room for reading, for dreaming, for music, for drama, for art, and simply for playing."