Britney Spears has come in for heavy criticism after a song surfaced on YouTube reporting to feature the singer without the aid of studio wizardry.

The audio clip is said to be a demo of the 'Alien', a song off the singer's eighth studio album 'Britney Jean' which was released last year. 

However, William Orbit, the song's producer, has jumped to Britney's defence on Facebook claiming that the singer was merely 'warming up'. 

He wrote: ”Dearest Music Lovers, I have heard that Britney vocal link that everybody’s been discussing. It has been impossible not to as there have been many comments directing my attention to it.

“I’d like to affirm that ANY singer when first at the mic at the start of a long session can make a multitude of vocalisations in order to get warmed up. Warming up is essential if you’re a pro, as it is with a runner doing stretches, and it takes a while to do properly. I’ve heard all manner of sounds emitted during warm-ups. The point is that it is not supposed to be shared with millions of listeners.

“A generous singer will put something down the mic to help the engineer get their systems warmed up and at the right level, maybe whilst having a cup of herb tea and checking through lyrics before the session really kicks off. It’s not expected to be a ‘take’. I think that 99% of you reading this will totally understand.

“Whomever put this on the internet must have done so in a spirit of unkindness, but it can in no way detract from the fact that Britney is and always will be beyond stellar! She is magnificent! And that’s that.”