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 Metro.co.uk 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.