The Canadian singer outsold label boss Justin Bieber by two to one, whose new single 'Boyfriend' lands at two.
'Call Me Maybe' sold over 110,000 copies in its second week on sale.
Bieber's mentor Usher grabbed his 13th UK Top 10 hit with his latest track 'Climax', which entered at four.
Gotye and Kimbra are a non-mover at three with the year's bestselling single so far 'Somebody That I Used To Know', while Nicki Minaj's 'Starships' completes the top five. Sean Paul falls to six with 'She Doesn't Mind' after three weeks at two.
fun. climb a massive 29 places from their midweek placing of 36 to seven with their huge US hit 'We Are Young', with Sway entering at eight with his new single 'Level Up'.
Breathe Carolina land at 21 with 'Blackout', while Jessie J and David Guetta's latest collaboration 'Laserlight' is a new entry at 26.
Alex Clare enters at 37 with 'Too Close', which currently features on a TV commercial for Internet Explorer.
John Legend returns to the top 40 with 'Ordinary People' at 27, after it was heavily featured in Saturday's (April 14) edition of The Voice UK.
Other retro tracks from Train ('Drops of Jupiter') and Wheatus ('Teenage Dirtbag') also climb back into the chart at 35 and 36 respectively.
Watch the video for Carly Rae Jepsen's 'Call Me Maybe' below:
Source: Official Charts Company
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