The song, which previously held the top spot for two weeks, climbs two to one on the tally following her performance on the MTV VMAs.
Meanwhile, Maroon 5's 'One More Night' lifts from three to two, fun. shifts five to four with 'Some Nights', and Pink reaches a new peak at six with 'Blow Me (One Last Kiss'.
Justin Bieber jumps nine to seven with 'As Long As You Love Me', and Alex Clare bounds 15 to ten with 'Too Close'.
Further down the chart, Swift's charity single 'Ronan' debuts at 16, Chris Brown finds a new peak at 24 with 'Don't Wake Me Up', and Alicia Keys lands at 37 with 'Girl On Fire'.
Frank Ocean vaults 78 to 39 with 'Thinkin' Bout You', Ne-Yo's 'Let Me Love You' scales from 58 to 50, and Kanye West, Jay-Z and Big Sean start at 55 with 'Clique'.
Elsewhere, Psy's 'Gangnam Style' enters at 64, and Brandy's 'Put It Down' bows at 90.
The top ten singles are as follows (click where possible for our reviews):
1. (2) Taylor Swift: 'We Are Never Ever Getting Back Together'
2. (3) Maroon 5: 'One More Night'
3. (1) Flo Rida: 'Whistle'
4. (5) fun.: 'Some Nights'
5. (4) Ellie Goulding: 'Lights'
6. (11) Pink: 'Blow Me (One Last Kiss)'
7. (9) Justin Bieber ft. Big Sean: 'As Long As You Love Me'
8. (6) Neon Trees: 'Everybody Talks'
9. (8) Owl City & Carly Rae Jepsen: 'Good Time'
10. (15) Alex Clare: 'Too Close'
Watch Swift's 'We Are Never Ever Getting Back Together' music video below: