Ariana Grande has branded her former boyfriend a "liar" after he accused her of cheating on him.

Grande announced her split from Australian singer Jai Brooks earlier this year (13) and it has now emerged he blames her new romance with The Wanted's Nathan Sykes for their break-up.

In a post on his Twitter.com page, Brooks writes, "Yes I was cheated on. Yes it does suck. Yes I was left for another man."

However, the former Victorious star has hit back at the comments, insisting Brooks is wrong.

Grande took to Twitter to send a message to her ex, writing, "Woke up this morning in complete and utter shock... I guess I shouldn't be so surprised... You said to me if I didn't come back to you, you'd make me look bad to the entire world... I'm no longer afraid of you or your lies anymore."

Grande went public with her relationship with British pop star Sykes last month (Sep13) after they were photographed holding hands and kissing during a date at Disneyland, California.