One week ahead of its release in stores, Britney Spears' new album Circus, has been posted online where fans can listen to it for free.

The album features 13 tracks by the pop star, including her latest single, Womanizer, as well as new tracks such as My Baby, Unusual You and Kill the Lights.

Womanizer was the biggest opening-week number by a female artist, beating Mariah Carey with Touch My Body.

The singer hadn't hit the top spot since her 1999 debut single Baby One More Time.

Britney has only had four tracks in the US top ten, including Toxic, Oops!...I Did It Again and You Drive Me Crazy.

Spears' album is among the most anticipated of the year as she rebounds from a tumultuous 2007 and early 2008.

Spears, 26, went through a bitter custody battle over her two sons last year, exhibited strange behaviour in public and by early 2008 was hospitalised twice for psychiatric evaluation.

But in recent months her father, Jamie Spears, has assumed control of her business and personal affairs, and Spears seems to have turned her life around. The ability to complete and promote Circus is an indicator of her apparent health.

The full album will be released in stores on December 2, Spears' 27th Birthday.

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