Children's author Jacqueline Wilson said on Monday she thinks young people are growing up too quickly, an opinion backed up by a survey showing over half of parents think childhood is over by the age of 11.

Teenagers are acting older at an "alarmingly young age," says Wilson, 62.

Among her best-known titles are "The Story of Tracy Beaker" about a 10-year-old growing up in a children's home and "Girls in Love", a tale of hairstyles, boyfriends and make-up.

The ICM survey of almost 1,200 parents with children aged under 18, by publisher Random House, found that more than half believe children are "young adults" at 11.

Almost three-quarters allow their children to drink alcohol before they are 18. Almost half allow their 16 year-olds to spend a night at their respective partner's house.

Fifty-three percent of teenagers under 16 are allowed to stay out later than 11 p.m. while more than two-thirds of pre-teen girls are allowed to get their ears pierced.

The survey was commissioned by the publisher to help launch Wilson's latest book: "My Sister Jodie".

"I feel it is a real shame that children act like adults at an alarmingly early age," she told The Times. "Because the narrators in my novels are teenagers, it may look as though I am pushing for teenagers to have more freedom.

"But it is not what I believe."

She urged parents to be stubborn in not giving in to their children's unreasonable demands.

"Parents need to take a stand, to tell their children 'I don't care if everyone else in the class is allowed to do this or that. You're not,'" she said.

"No one wants a confrontation but adolescence is a tricky time and it is the nature of the beast that teenagers are a bit stroppy. You just have to accept that."