Lady Gaga's much-hyped cover of White Christmas has been leaked on YouTube.

The Bing Crosby classic was set to be released by Gaga as part of her festive-themed EP, A Very Gaga Holiday, this weekend.

But copies of it appeared online over the last few hours, revealing that the Born This Way star has added an extra verse onto the sappy Christmas favourite.

Stopping midway through the tune to explain her extension, Gaga says, "So as you can tell, I'm very outgoing and a little bit shy, but I've decided that this song is just too short. It's such a beautiful Christmas song but it's only one verse, so I added one extra one. Here it goes."

The singer then goes on to croon about her dreams of a "white snowman... with a carrot nose and charcoal eyes."

She ends the song with, "OK, so I suppose it's not really white outside."

A Very Gaga Holiday will be released digitally and includes a cover of Nat King Cole's Orange Coloured Sky, as well as acoustic versions of You And I and The Edge Of Glory, from Gaga's album Born This Way.

Bing Crosby first sang White Christmas in 1941. It has sold over 50 million copies worldwide and continues to be one of the biggest hits of all time.

Watch Gaga's take on the festive anthem in the video, below.

Gaga's cover of White Christmas leaked