Britney's 'Telephone' leaks onto web?

A demo supposedly of Britney Spears singing Lady GaGa's 'Telephone' has leaked onto the internet.

Rodney Jerkins, aka Darkchild, who produced the song, revealed last year that himself and GaGa had written the song for Spears's Circus album, but it never made the final cut of the LP.

He posted on Twitter: "Me and Lady Gaga wrote a smash for Britney called 'Telephone' the label didnt out (sic) it on the lp. It should be out right now!!! Its too hot!!!"

Jerkins recently promised that he would leak Spears's version of the song, which reached number one in the UK singles chart with Lady GaGa, but later changed his mind.

He tweeted: "I will [leak the song] but i cant do it today. It has to be the right time. I have to keep Britney happy but it will come out," later writing: "Im not gonna leak it becuz i thought about it, it would be disrespectful to Britney. She didnt wanted to come out, I respect that (sic)."

Yesterday a clip claiming to be a demo version of Spears singing 'Telephone' was posted on YouTube. After suggestions that the demo may be a fake, website Gimme Britney reports that GaGa's label Sony Records is "not all that worried" about the leak.