The 80 year old, who played the masked villain in the original Star Wars trilogy, can no longer walk unaided after an operation left him with issues in his right leg.

"Today I am a shadow of my former self. I can barely walk and struggle to even remember what I did yesterday," he tells Britain's The Sun newspaper.

"I had an operation on both my hips ages ago and although the hip replacement is OK, my right leg won't straighten properly... As a result I can't walk two yards without crutches. I can't put any pressure on my leg. If it's a distance then I have to get wheelchair assistance."

Last year (14), Prowse revealed he is suffering from dementia, and now admits the condition is getting worse.

"My memory is not much better either. I filmed Star Wars nearly 40 years ago and I can't really remember any of it," he adds. "I can't even remember what I did yesterday, let alone last week... I haven't been diagnosed with Alzheimer's, but it's very hard for me."

Prowse, who beat prostate cancer in 2010, played Darth Vader onscreen but his voice was dubbed by James Earl Jones. The character was killed off at the end of the original trilogy, but Prowse was still surprised he was not asked to be involved in the latest film The Force Awakens.

He says, "I have never had a call from anyone to be in the new movie. Nobody even bothered to get in contact to ask me about my association with this movie."

Prowse fell out with Star Wars creator George Lucas in the 1980s after the actor was accused of leaking a spoiler unveiling Darth Vader as Luke Skywalker's father in The Empire Strikes Back.

Star Wars: Episode VII - The Force Awakens, directed by J.J. Abrams, is released in the U.S. and U.K. this week (beg14Dec15).