Tulisa Contostavlos once threatened by stalker

Singer Tulisa Contostavlos was terrified by a stalker in the middle of a night recently.

The 24-year-old was left petrified earlier this week after a 24-year-old man managed to get past the security at her six million pounds-worth mansion in Hertfordshire, Southern England, and demanded to see her.

Contostavlos sent her personal assistant Gareth Varey to answer the door and what followed was a heated exchange of words, reports contactmusic.com.

"He started knocking down her front door in the middle of the night and Tulisa was utterly petrified. This is the last thing she needs to be dealing with right now.She has had an absolutely hellish past few days - and now this," said a source.

The source added the unnamed assailant had started to harass the singer in the wake of her arrest for allegedly helping to fix a cocaine deal earlier this month.

"She is at an all-time low. Tulisa is a girl whose professional life is in tatters. This guy started hounding her daily since the drug fixing story broke," the source added.