Sir Ian McKellen, who played Gandalf in the Lord of the Rings films, has voiced dismay over the decision to drop Peter Jackson as director of The Hobbit.
Sir Ian played the wizard Gandalf in Lord of the Rings
"I'm very sad as I should have relished revisiting Middle Earth with Peter again," the actor wrote on his website.
"It's hard to imagine any other director matching his achievement in Tolkien country."
Jackson refused to discuss working on the Hobbit until a DVD royalty dispute with New Line Cinema was settled.
But New Line said it had only "limited time" to make the film and was proceeding without the Oscar-winning director.
The announcement has led to an online petition of 1,100 people asking for Jackson to be reinstated.
The petition created calls for The Hobbit to be filmed "the way it was meant to be or not at all".
A website has also been set up urging a boycott of New Line, and fans have used weblogs and forums to question the studio's judgement.
The petition argues that a Hobbit movie without Peter Jackson and his writers and special effects team is not what fans want.
"The characters and scenery will all be new and unfamiliar and props, costumes, and the backdrop of New Zealand will all be lost," it said.
"Most likely even the original actors will not sign on to do it - can you imagine someone other than Ian McKellen playing Gandalf the Grey?"
A user of fan site theonering.net has registered the domain name boycottnewline.com, which links to another petition.
"Something must happen to get New Line and Jackson to talk about the [legal case], which has been hanging over future Tolkein-related productions since 2005," the owner has written.
"The only way to get New Line to budge is to boycott future New Line productions until they sit down and hash things out with Peter Jackson."
Before the story emerged this week, there was already a site - thehobbitfilm.com - encouraging fans to ask top studio executives to get on with making the movie with Jackson.
It urged people to send letters or postcards because "the only way we are going to reach our goal of having a live-action version of The Hobbit from Peter Jackson and his team is by keeping after the studios who own the rights".
However, other fans were more relaxed about the way the project was progressing.
"That's the best news I've heard concerning Peter Jackson in about five years," wrote one person on the ringbearer.org site.
"He's exactly the wrong guy to handle The Hobbit in any way shape or form."
Another, on theonering.net, said: "I'm sure The Hobbit will turn out to be a success even without the help of the great Peter Jackson."
A spokesman for distributor MGM told Variety newspaper that the matter was "far from closed", leaving some people hoping Jackson would return.
"Hopefully they will see the light and involve the two people who have proven worth in telling the stories," one person wrote in the chatroom at theonering.net.
Neither New Line nor MGM was available for further comment.