Clarkson most successful 'Idol' winner

Kelly Clarkson is the most successful winner of American Idol, according to Billboard.

The music publication reports that Clarkson, who won the first series of the show, has so far sold 10.6m albums, 15.9m singles and had 4.2m radio plays.

Country star Carrie Underwood, who won Idol's fourth season in 2005, is the second most successful contestant.

Despite the 'All-American Girl' singer having sold more albums than Clarkson at 11.5m, her singles and radio spins are lower at 13.9m and 2.4m respectively.

Rounding out the top three is Chris Daughtry, whose band Daughtry has sold 5.7m albums. The singer-songwriter finished in fourth place on the programme's fifth season.