In an interview with the Telegraph, the actor, who played Aragorn in the trilogy, described the process of making the films as sloppy, and suggests if the first movie wasn't such a success, the final two "would have been straight to video".
"Anybody who says they knew it was going to be the success it was, I don't think it's really true," he said.
"They didn't have an inkling until they showed 20 minutes in Cannes, in May of 2001. They were in a lot of trouble, and Peter [Jackson] had spent a lot. Officially, he could say that he was finished in December 2000 - he'd shot all three films in the trilogy - but really the second and third ones were a mess. It was very sloppy - it just wasn't done at all. It needed massive reshoots, which we did, year after year.
"But he would have never been given the extra money to do those if the first one hadn't been a huge success. The second and third ones would have been straight to video."
Mortensen picks The Fellowship of the Ring as the film that turned out the best of the three, because it was shot in one go. Mortensen was only hired when Stuart Townsend, the original actor in the role of Aaragon, was fired days before shooting began.
"It was very confusing, we were going at such a pace, and they had so many units shooting, it was really insane. But it's true that the first script was better organised," he says.
Mortensen went on to describe Jackson's use of special effects in his films as overdone, removing the subtly of the stories.
"Also, Peter was always a geek in terms of technology but, once he had the means to do it, and the evolution of the technology really took off, he never looked back. In the first movie, yes, there's Rivendell, and Mordor, but there's sort of an organic quality to it, actors acting with each other, and real landscapes; it's grittier.
''The second movie already started ballooning, for my taste, and then by the third one, there were a lot of special effects. It was grandiose, and all that, but whatever was subtle, in the first movie, gradually got lost in the second and third. Now with The Hobbit, one and two, it's like that to the power of 10.
"I guess Peter became like Ridley Scott - this one-man industry now, with all these people depending on him," he said.
"But you can make a choice, I think. I asked Ridley when I worked with him (on 1997's GI Jane), 'Why don't you do another film like The Duellists [Scott's 1977 debut, from a Joseph Conrad short story]?' And Peter, I was sure he would do another intimately scaled film like Heavenly Creatures, maybe with this project about New Zealanders in the First World War he wanted to make. But then he did King Kong. And then he did The Lovely Bones - and I thought that would be his smaller movie. But the problem is, he did it on a US$90million (NZ$103.8 million) budget. That should have been a US$15million movie. The special effects thing, the genie, was out of the bottle, and it has him. And he's happy, I think..."
