Harry Potter fans in battle to save their hero from clutches of Coca-Cola

One month before the release of the first Harry Potter film, a campaign in the United States is bombarding J K Rowling with protest letters and e-mails accusing the author of capitulating to corporate greed by granting Coca-Cola exclusive rights to market her creation across the globe.

Fans of her books have joined forced with a health advocacy group called the Center for Science in the Public Interest to denounce the pairing of the world's best-known purveyor of fizzy drinks with Rowling's magical world of wizards, owls and muggles. Just when the world's children have been given a reason to fall in love with reading, the campaigners argue, they are now being bombarded with the worst kind of tie-in promotion.

"The bottom line is that an adored literary phenomenon is being put to work to sell more junk food," said Michael Jacobson, CSPI's executive director and founder of a website called SaveHarry.com.

In February, Coca-Cola announced a $150m (£100m) exclusive marketing agreement with Warner Brothers, the studio releasing Harry Potter and the Philosopher's Stone in Britain and the United States on 16 November. According to Mr Jacobson, Rowling's personal stake in the deal could be as high as £10m.

Already Coca-Cola products – both its fizzy drinks and its healthier fruit varieties – have been emblazoned with images from the film. The deal has some soft edges: Harry himself cannot be depicted drinking Coke, and there is no product placement in the film itself, which stars Daniel Radcliffe as Harry alongside Robbie Coltrane, Maggie Smith, Richard Harris, Richard Griffiths, Fiona Shaw, Ian Hart and Alan Rickman.

An e-mail posted on the SaveHarry.com site implores Rowling to reconsider her involvement. "Coke and other soft drinks are JUNK, and certainly not what Harry would want kids to drink," the text reads. "Please, Ms Rowling, help us Save Harry -- and protect children's health. Donate the royalties from the deal to fund nutrition campaigns, and stop all future sponsorship by Coca-Cola."

In the past, the author of the Harry Potter series – which, in print form, has reached volume four of a projected seven and sold tens of millions of copies worldwide – has declared herself fiercely protective of her creation and wary of commercial exploitation.

One letter posted on the SaveHarry.com site reminded her of this. "It seemed that there was someone with ethics and thinking beyond the almighty dollar," said the letter, signed Sarah W. "It saddens me that it comes down to money rather than what is right and better for society."

This is not the first time Coca-Cola's marketing strategies have proved unpopular. A campaign to have Coca-Cola vending machines installed in American schools in exchange for sponsorship money has been widely criticised.

The company has donated $18m (£12.4m) to a three-year literacy campaign as part of the Harry Potter deal. "These efforts," a recent company statement said, "will centre on helping people discover the magical world of their imaginations through reading while reinforcing the core values and attributes shared by Harry Potter and Coca-Cola."

No explanation is offered about what those "core values and attributes" involve.

JK Rowling said: "I understand that Coca Cola's global literacy cause will focus on increasing children's literacy – a cause of particular interest to me."