The X Factor Australia judge's track leads the tally for a second week, fending off competition from Justice Crew's 'Boom Boom', which remains at number two.
Meanwhile, Taylor Swift leaps 13 to three with 'We Are Never Ever Getting Back Together', Birdy debuts at four with 'Skinny Love', and The Script and will.i.am's 'Hall Of Fame' lands at seven.
Far*East Movement and Cover Drive's 'Turn Up The Love' bounds from 14 to eight, and Florence + the Machine's 'Spectrum' rounds out the top ten.
Further down the chart, Birdy's 'People Help The People' lifts 20 to 13, Chiddy Bang's 'Mind Your Manners' vaults 26 to 17, and Jason Derulo's 'Pick Up The Pieces' bows at 37.
Elsewhere, Duffy's 'Mercy' rebounds at 41, and Wiley's 'Heatwave' starts at number 44.
The Top 10 singles in full (click where possible for our reviews):
1. (1) Guy Sebastian ft. Lupe Fiasco: 'Battle Scars'
2. (2) Justice Crew: 'Boom Boom'
3. (13) Taylor Swift: 'We Are Never Ever Getting Back Together'
4. (*) Birdy: 'Skinny Love'
5. (3) Maroon 5: 'One More Night'
6. (5) Owl City ft. Carly Rae Jepsen: 'Good Time'
7. (*) The Script ft. will.i.am: 'Hall Of Fame'
8. (14) Far*East Movement ft. Cover Drive: 'Turn Up The Love'
9. (4) fun. 'Some Nights'
10. (6) Florence + the Machine: 'Spectrum (Say My Name)'
Listen to Guy Sebastian's 'Battle Scars' below: