Tulisa Contostavlos is on trial for allegedly assaulting a blogger.
Asked by her barrister Jeremy Dein QC if she assaulted Mr Morgan, Contostavlos said: "Most definitely not."
Mr Dein asked about a sex tape of Contostavlos which was leaked to the press.
She said she found out Mr Morgan may have been involved in this, adding: "I couldn't confirm at the time that he was involved because I didn't know at the time the tape existed.
"Once I knew, a couple of details made me believe he was involved a lot more than he made out."
Describing the publication of the sex tape, she went on: "I was horrified - it was one of the worst times of my life.
"I recorded a video on YouTube explaining the situation and put it up online and posted it on my Twitter account.
"An ex-boyfriend had taken what was supposed to be private footage of us and many years later tried to sell it and put it online."
Singer Tulisa was "upset, but not angry" after a confrontation with a celebrity blogger in Chelmsford, her tour manager has told a court.
Singer Tulisa Contostavlos told police allegations she assaulted a celebrity blogger are part of a vendetta against her.
Tulisa Contoslavos has appeared Chelmsford Magistrates Court on assault charges.