(File image) Kim Kardashian

London - Spencer Pratt says Kim Kardashian is the “world's most famous porn star”.

The former Hills star - who is married to Heidi Montag - claims the only reason Kim is famous is because a sex tape of her and her former boyfriend Ray J leaked in 2007.

He said: “No one can understand why she is famous but I can, that is why she is famous! People are so interested in asking why she is famous that it's just an endless cycle.”

“But I can tell you that Kim Kardashian is the world's most famous porn star! She would not be anywhere, I guarantee it, without that sex tape.”

However, Spencer claims he doesn't feel threatened by Kim and her family, who have their own reality TV show Keeping Up With The Kardashians.

He added: “It's like any royal family, she is just from a different royal land. Kim Kardashian is from Mars and we're from Earth, you know what I mean?”

Meanwhile, Spencer has blasted celebrities including Justin Bieber and Harry Styles as self-obsessed.

He said: “They are all too famous and can't handle it, especially with websites like Twitter and Instagram, it's hard to stay humble.”

“What's Justin Bieber been doing today? Probably posting photos of his ass on the Internet.”

“The plot is gone and they have lost their scripts.” - Bang Showbiz