The 55-year-old actor described the process of making the Peter Jackso-directed film as more or less complete chaos, reported Daily Telegraph.
"They were in a lot of trouble, and Peter 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," Mortensen said.
Mortensen said that 'The Fellowship of the Ring' was the best film out of the three because it was shot in one go.
"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 said.