Liam Payne asked an X Factor stylist to sit on his lap when he was just 17, it has been claimed.
Grace Woodward, who worked as the ITV show's fashion director in 2010, says it happened because she had been linked to eventual winner Matt Cardle.
Addressing her time on the programme, the wardrobe boss also hit out at the show's 'dark misogyny'.
The series spawned global sensation One Direction, with Liam, Harry Styles, Zayn Malik, Louis Tomlinson and Niall Horan enjoying worldwide success.
A spokesperson for the talent finding show says the allegations are "unsubstantiated".
Speaking to The Sun, Grace said: "When he asked me to sit on his lap it was light-hearted. But how many ordinary 17-year-olds would ask that of someone working with them in a professional capacity? But no one said a word.
"To me it was always evident that the One Direction boys were treated differently. They were set apart from the rest from the start."
Mirror Online have reached out to Liam's reps, who declined to comment.
She previously told how the programme's female stars struggled under the pressure while "male contestants felt they were untouchable".
Grace said she even had a spat with Cheryl when they argued over one of Rebecca Ferguson's costumes.
Last year, ITV confirmed that The X Factor has been axed after 17 years.
There are no plans to bring it back, despite music mogul Simon Cowell saying we haven't seen the last of the long-running Saturday night show yet.
Following the claims, the X Factor released a statement.
A spokesman said: "These allegations are unsubstantiated, dating back 12 years on a show that is no longer in production or on television.
"The wellbeing of everyone involved in any of our programming is paramount and we have thorough and robust duty of care protocols in place to provide support for anyone who may need it including psychologists on hand to provide expert opinion.
"If we are made aware of any concerns, we treat the issue seriously and investigate immediately."
Earlier this month, it emerged show boss Cowell and his entertainment company Syco had been hit with legal claims by former contestants who claim they did not have proper care.