The group are currently working on new material, which Duncan James confirmed would be released next year along with a tour.
On his Twitter account Simon Webbe wrote: "Just found out blue demo has been leaked onto YouTube, not cool! (sic)
"People who do that sort of thing have no respect for the writer, producer, Blue and most of all music.... its straight stealing...."
Lee Ryan, who will release his second album later this year, added: "It sucks that blues new songs are out there already! It really ruins the anticipation and excitement of music and I feel this is very sad!"
Meanwhile James, currently a judge on Five's Don't Stop Believing, was confused as to how the leak had occurred.
"Found out that some of the new blue demo's have leaked out onto the net and don't understand how!!!! WTF!" he wrote.
> Duncan James: 'No more Blue spit roasts'