The US singer-songwriter climbs four places to claim the top spot, fending off competition from Enrique Iglesias, who moves three to two with 'Tonight (I'm Lovin' You)'.
Last week's number one - Guy Sebastian's 'Who's That Girl' - slips to four, Alexis Jordan's 'Happiness' leaps from 13 to six, and Britney Spears's 'Hold It Against Me' debuts at number ten.
Elsewhere, Katy Perry lands at 12 with 'E.T', and the Lonely Island's 'I Just Had Sex' vaults 36 to 15.
Martin Solveig and Dragonette's 'Hello' advances 29 to 21, while Kanye West's 'All Of The Lights' enters at 46.
The top ten singles in full (click where possible for our reviews):
1. (5) Wynter Gordon: 'Dirty Talk'
2. (3) Enrique Iglesias ft. Ludacris & DJ Frank E: 'Tonight (I'm Lovin' You)'
3. (2) Bruno Mars: 'Grenade'
4. (1) Guy Sebastian ft. Eve: 'Who's That Girl'
5. (4) Chris Brown: 'Yeah 3X'
6. (13) Alexis Jordan: 'Happiness'
7. (9) David Guetta ft. Rihanna: 'Who's That Chick?'
8. (7) Black Eyed Peas: 'The Time (Dirty Bit)'
9. (6) Katy Perry: 'Firework'
10. (*) Britney Spears: 'Hold It Against Me'