Former Spice Girl Geri Halliwell has been crowd the most successful female celebrity children's author of 2008.

Halliwell's six book series for children, Ugenia Lavender, tells the adventures of a nine-year-old girl.

The first title, released in May, was praised by critics, with the Independent on Sunday calling in “inspirational” and “totally ingenious”.

Rachel Airey, head buyer at WH Smith, said Halliwell's series has continued to sell well as the remaining titles have been released.

“Continued strong sales prove that customers are buying this series because it's well written and both the kids and their parents love it,” Ms Airey told booktrade.

“The amount of time Geri has given to the promotion of these books shows her dedication and commitment to the series.”

The sixth book in the Ugenia Lavender series is released today (October 3rd).