Earlier this week, distributor Harvey Weinstein announced that the movie is to be re-cut in order to appeal to a wider audience.
The Australian actor told The Hollywood Reporter that the context of King George VI's attempt to conquer his speech impediment will be altered if foul language is removed.
"I just think it's a shame considering that it's all in the context of therapeutic play," he said.
Rush added that audiences likely would not object to the swearing because it is not presented in an "offensive" manner.
He explained: "It's almost like a tongue-twister. It's gobbledygook. But it's not aggressive, it's not offensive. It's not harmful… If you cut it, then you're going to cut one of the key thrills of the film."
The film's director Tom Hooper also insisted that he does not support excising material from The King's Speech.