Alexandra Burke has held on at the top of the singles chart for a second week, The Official Charts Company said.
Start Without You featuring Laza Morgan is the X Factor winner's third chart topper since she won the fifth series of the ITV talent show in 2008. It follows success with singles Hallelujah and Bad Boys and a number one debut album, Overcome, in October last year.
Taio Cruz climbed one place to number two with Dynamite while Katy Perry's Teenage Dream slipped a place to number three.
Dublin band The Script were down one to number four with For The First Time and X Factor runner-up Olly Murs - in top spot two weeks ago - was down to fifth with Please Don't Let Me Go.
The highest new entry was Shontelle's Impossible.
In the album chart The Script were straight in at number one with Science And Faith. It is the second album for Danny O'Donoghue, Mark Sheehan and Glen Power.
New entries also took up the next three spots, with Linkin Park's A Thousand Suns, Robert Plant's Band Of Joy, and Phil Collins' Going Back, in at two, three and four.
Last week's number one album, Flamingo, the debut solo effort from the Killers' Brandon Flowers, slipped to number five while Mercury Prize winners XX dropped three places to number six.