Britney Spears denies lip-synching rumours

London: Britney Spears has hit back at her lip syncing rumours, insisting that she is undergoing "grueling" vocal training for her upcoming Vegas `Britney: Piece of Me` show.

Her spokeswoman told that she wants to make sure she can handle 48 live concerts when her shows kick off at the 4,600-seater Planet Hollywood venue in December.

Spears will rake in 200,000 pounds a night for her shows.

Earlier she was accused of being paid a lot of money just to lip-sync.

The insider told the New York Daily News that the `Toxic` hitmaker hasn`t sung live for a couple of years.