Welsh singer Duffy has recorded her first ever number one single with Mercy.
Based on download sales alone, Mercy went straight in at the top spot.
US band Nickelback remained at number two in the charts with Rockstar, while Basshunter's Now You're Gone slipped to third after five weeks at number one.
Elsewhere, David Jordan moved up one place from fifth to fourth with Sun Goes Down.
Adele's Chasing Pavements and Rhianna's Dont Stop The Music both fell two spots from third and fourth to fifth and sixth.
H two O, Kelly Rowland, The Feeling and Goldfrapp made up the top ten.
In the album chart, Jack Johnson claimed the number one spot for the second week running with Sleep Through the Static.
Nickelback's All the Right Reasons stayed in second place.
The reissue of Michael Jackson's famous Thriller album, celebrating its 25th anniversary, charted in third.
Thriller 25 includes the original tracks as well as new tunes from hip-hop artists Kayne West and Will.i.am.
Adele's 19 and Morrissey's Greatest Hits were fourth and fifth in the UK album chart respectively.