Ariana Grande has responded to a message posted online by former boyfriend Jay Brooks that claims she cheated on him with Nathan Sykes.

The US star is said to have dated Janoskians member Brooks from August 2012 to earlier this year.

Grande has since begun a relationship with The Wanted's Nathan Sykes - but a new Twitter post by Brooks claims she cheated on him with the 'Glad You Came' man. He said:

"Nathan may be a top bloke or a sweet person, but what he did was just completely wrong. He interfered with my life and did not respect my relationship, his actions caused me to not be able to sleep at night and not see the world as a beautiful place."

Grande has since replied, tweeting: "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. I'm going to be the lady my mother raised and carry myself with class and dignity... But I will never be any man's press opportunity."

She added: "Girls... RESPECT YOURSELVES. Keep your head held high and speak only kind words. Know your truth... no one can ever take that away from you. It's always ok to defend yourself. My fans know what kind of person I am. Never let any man discredit u or the values you were raised with. I'm finally happy. Words can't hurt me anymore."

Grande and Sykes meanwhile recorded the duet 'Almost is Never Enough' for the former's latest album 'Yours Truly'.