By Darren Waters
BBC News Online entertainment staff
Harry Potter author JK Rowling has given her blessing to fans who write their own Potter stories online.
The latest Potter film comes out in the UK on 31 May
Thousands of fans have written their own stories based on the world of Harry Potter, which are published on the net.
The release of the third Potter movie is expected to boost the already hugely-popular fan fiction phenomenon.
A spokesman for Rowling's literary agent said she was "flattered people wanted to write their own stories" based on her characters.
Websites such as FanFiction.net and SugarQuill.net carry thousands of stories inspired by Rowling's global best-sellers.
The Potter writers have invented a wealth of new adventures, developed new relationships and taken the
characters in directions perhaps never imagined by Rowling herself.
The spokesman for the Christopher Little literary agency said: "JK Rowling's reaction is that she is very flattered by the fact there is such great interest in her Harry Potter series and that people take the time to write their own stories.
"Her concern would be to make sure that it remains a non-commercial activity to ensure fans are not exploited and it is not being published in the strict sense of traditional print publishing."
He said writers had to ensure that the stories were not obscene and were credited to the author and not to JK Rowling.
He said: "The books may be getting older, but they are still aimed at young children.
"If young children were to stumble on Harry Potter in a an x-rated story, that would be a problem."
Fan fiction is a genuine online phenomenon, but its roots go back decades.
Dr Matt Hills, lecturer in media and culture studies at Cardiff University and author of Fan Cultures, said fan fiction had always been part of fan culture.
A new Potter film is released on 31 May
"It's something that fan cultures have always been involved in.
"The arrival of online means it has a greater visibility.
Before the age of the internet, it was only circulated between fans."
TV programmes such as Doctor Who, Buffy the Vampire Slayer and Star Trek are among the most popular sources of fan fiction.
But recent films such as Pirates of the Caribbean and video games such as Halo have also inspired people to write their own stories.
Dr Hills said for a lot of fans it was about being more than just a "passive spectator".
"Fans have a great affection for their objects of fandom. They love these films and programmes and characters and this spurs them on.
"It's a fascination with characters who are central to programmes and fans want to explore the afterlives of these characters and explore their back stories."
Dr Hills said fan fiction began with early science fiction but took off when fans of Star Trek began writing their own stories.
But not all authors are as happy to have their work used as the basis for amateur writers' own musings.
Xing Li, editor of FanFiction.net, said the website had received a number of requests from authors to remove work.
He said: "It is our long standing policy of fanfiction.net to respect the wishes of
original writers and will remove or ban fan fiction categories at their
Authors to have contacted the website include Anne Rice, Anne McCaffrey and Raymond Feist.
The spokesman at the literary agency stressed that copyright in the Harry Potter series and characters remained with Rowling and trademarks with Warner Bros.
"Hopefully the fan fiction will help people become writers in their own right," he said.