Styles has been rumoured to be in a relationship with the Inbetweeners actress, after they were spotted together earlier this week.
© WENN / Manuil Yamalyan
© Rex Features
However, Tomlinson has dismissed reports suggesting that they were in a serious relationship.
He made the comments while discussing which of the One Direction members got the most female attention while on tour.
"Do I even need to say who?" Tomlinson is quoted as saying in The Mirror. "I think it would be completely and utterly unfair to single out girls in that way, or put it like that.
"But... if you were to put it like that, I think it would - possibly - be... Harry. Do we keep a tally? No, we do not! That's hideous."
© Rex Features / Shropshire Star/NTI Media Ltd/Rex Features
When asked if Styles was still dating Atack, he added: "No, no..."
One Direction have been completing their second LP in Stockholm during the past few weeks and fly to the US this week for their three-month, 62-date tour.
Styles has previously been romantically linked to 18-year-old model Emma Ostilly and 24-year-old Irish photographer Sarah-Louise Colivet.
Watch the video to 'What Makes You Beautiful' by One Direction below:
