Media playback is unsupported on your device Media caption Author Jacqueline Wilson says she still uses her teenage diaries as inspiration

Keeping a diary helps boost children's writing skills, according to research from the National Literacy Trust.

And children's author Jacqueline Wilson agrees diary writing "increases your fluency and helps you become more comfortable at expressing yourself".

The Tracy Beaker author says she herself wrote a diary from the age of seven or eight and continued through her childhood and into her teens.

She is backing a campaign for children to be given diaries this Christmas.

Hopes and ambitions

Ms Wilson told BBC Breakfast she thinks writing a diary has a massive advantage over social media when it comes to expressing innermost thoughts and feelings.

The point is diaries are "not for sharing", she argued.

"You don't care how many people like it. It's just for you. You can write anything you want down."

A diary entry could be an account of your day, what you really feel about people you absolutely love, or people you hate, your hopes and ambitions, she said.

And if you are really into sport you can use the diary for detailed accounts of matches you have watched, she suggested.

Tracy Beaker is partly written in diary form and Ms Wilson says she still uses her teenage diaries as a source of inspiration in some of her writing... even though "they are terribly embarrassing to look back on... you care so passionately about things."

Other famous diaries in children's literature are:

Jeff Kinney's Wimpy Kid,

Anne Fine's Killer Cat

and Meg Cabot's Princess Mia

For older readers there are the works of Samuel Pepys, James Boswell, Virginia Woolf and Anne Frank - and on a rather more frivolous note: Bridget Jones.

Image copyright Thinkstock Image caption Girls are more likely to keep diaries than boys, the research found

Data on more than 3,000 eight-to 11-year-olds, collected by the charity, suggests that pupils who keep a diary are almost twice as likely to write above the expected level for their age (27.1%), compared with children who do not (15.5%).

The main attraction of writing a diary is being able to choose the subject matter and 82% of girls and 76% of boys told the researchers that writing is more fun if they are allowed to decide what to write about.

The research also found:

girls are three times as likely as boys to keep a diary

almost a third of eight-to 11-year-olds write diaries

almost half of children write in private, even if they do not keep regular diaries.

National Literacy Trust director, Jonathan Douglas, said the charity was "encouraging parents, families and anyone buying a gift for a child or young person this Christmas to give the gift of a diary.

"You'll be giving them a platform to express themselves through words and the tools to become a better writer and do well at school. And you never know - your child could produce the next Diary of a Wimpy Kid!"