Britney Spears has been forced to reduce the ticket cost of her UK concert dates after low sales, it has been reported.

The singer will start the UK leg of her 'Femme Fatale' tour in London later this week, but has had to cut the price of her tickets after the shows failed to sell out.

According to The Sun, promoters have slashed the price of Spears's tickets to £30 from £55 for her Birmingham LG Arena date.

Organizers are said to be worried after initial sales of tickets may see the 16,000-capacity venue half-full for when the 29-year-old takes to the stage early next month.

Meanwhile, promoters have been running a buy one get one free offer for the concert in Sheffield, branding it a 'bonfire night offer' when Spears plays the city's Motorpoint Arena on November 5.

However, organizers have said that the reduced prices were "segmented marketing to reach new consumers".

Britney Spears will officially release her new single 'Criminal' in the UK on November 21.