The star heads the midweek chart with her international hit 'Call Me Maybe' and keeps label boss Justin Bieber at number two with 'Boyfriend'.
Bieber's mentor Usher trails the pair at three with his latest single 'Climax', while Nicki Minaj is at four with 'Starships' and Gotye is at five with 'Somebody That I Used To Know'.
Sway is at seven with 'Level Up', Chris Brown takes 11 with 'Turn Up The Music' and Azealia Banks is at 12 with '212'.
Jason Mraz is at 20 with 'I Won't Give Up', Jay-Z and Kanye West are 21st with 'Paris' and Breathe Carolina are a new entry at 23 with 'Blackout'.
The Rainbow Mix tribute song to fun.'s 'We Are Young' is new at 33, while the original version trails at number 36.
Over on the album chart, Alabama Shakes take the lead with their new record Boys & Girls, while Adele advances to number two with 21.
Nicki Minaj slips to three with Pink Friday: Roman Reloaded, Jessie J is at four with her debut album Who You Are and Emeli Sandé remains at five with Our Version Of Events.
> View the current singles top 100 here
Watch the music video for Carly Rae Jepsen's 'Call Me Maybe' below: