The track, which marks the singer-songwriter's first solo single release, notches up a third week at the chart summit, fending off competition from Enrique Iglesias's 'Tonight (I'm Lovin' You)', which remains at number two.
Meanwhile, Rihanna vaults from 27 to three with 'S&M', and Katy Perry's 'E.T' leaps from 11 to five.
Further down the chart, Usher jumps from 23 to 16 with 'More', while Pink advances 34 to 22 with 'F**kin' Perfect'.
Far*East Movement's 'Rocketeer' lands at number 30, and Diddy-Dirty Money's 'Coming Home' enters at 49.
The top ten singles in full (click where possible for our reviews):
1. (1) Wynter Gordon: 'Dirty Talk'
2. (2) Enrique Iglesias ft. Ludacris & DJ Frank E: 'Tonight (I'm Lovin' You)'
3. (27) Rihanna: 'S&M'
4. (3) Alexis Jordan: 'Happiness'
5. (11) Katy Perry: 'E.T'
6. (6) Bruno Mars: 'Grenade'
7. (5) Guy Sebastian ft. Eve: 'Who's That Girl'
8. (7) Chris Brown: 'Yeah 3X'
9. (8) David Guetta ft. Rihanna: 'Who's That Chick?'
10. (4) Britney Spears: 'Hold It Against Me'