Related information: Read Rowling's foreword for the book, published in June of 2002.

J K ROWLING is to contribute a new work, which marks her first departure from children's fiction, for a book of short stories that is being compiled by Sarah Brown, the wife of the Chancellor of the Exchequer.

The author made it clear to friends this week that Harry Potter will definitely not be involved in the new story. The book is being compiled to raise money for The National Council for One Parent Families. The theme of the book will be magic and it is expected to be published in spring next year.

In another literary coup for Mrs Brown, the book will bring Adrian Mole, the angst-ridden diarist created by Sue Townsend, out of retirement. Although Townsend recently pledged not to revive her awkward anti-hero, it is understood that Adrian Mole will make one last comeback as a children's entertainer and magician in a short story for the collection.

Mrs Brown's achievement in persuading Rowling to contribute to the fund-raising project will be considered a triumph by the Labour Party and increase speculation that the author has become very close to Gordon Brown and his supporters.

The Telegraph reported that last year Rowling was asked to endorse the Labour Party by Mr Brown, whose wife runs the successful public relations company Hobsbawn and Macaulay. The Chancellor's approach to Rowling was made when they both addressed the conference of the National Council for One Parent Families.

Rowling, 34, a single mother who struggled financially before her first book was published in 1997, is known to have some Left-leaning sympathies, but is also fiercely independent. Her publishers Bloomsbury are keen for her to remain politically neutral, but were delighted with her decision to join the team of up to eight other female contributors for the book.

Rosemary Davidson, an editor at Bloomsbury, said last night that the firm was unsure if Rowling's story would be an extended foreword or if it would be among the other short stories in the main body of the book. The book will be eagerly awaited by an estimated 14 million Rowling fans who include William Hague, the Tory Party leader.

Rowling campaigns passionately for the National Council for One Parent Families as an ambassador and patron. Last October she attacked the Government's policy on one-parent families. She said that Labour could do "a good deal more" and set an example by donating £500,000 to the charity.