Broadway star Gerard Canonico is the latest former colleague of Lea Michelle to hit out at her behind-the-scenes behaviour.

The 33-year-old has been under fire for the last few days after her former Glee co-star Samantha Marie Ware accused her of making her time on the show "a living hell".

After Ware's claims made headlines, Michele posted a lengthy message on Instagram apologising for her past "immaturity" and how her behaviour may have been "perceived" by her co-stars.

The move appears to have backfired, however, with multiple former colleagues replying to admonish her publicly, including Canonico, who worked as an understudy on the Broadway musical Spring Awakening.

"You were nothing but a nightmare to me and fellow understudy cast members," he wrote.

'You made us feel like we didn't belong there. I tried for years to be nice to you to no avail.

"Maybe actually apologize instead of placing the blame on how others 'perceive' you. You'll probably just delete this though."

Glee star Heather Morris has also spoken out on the issue, admitting that Michele was "unpleasant to work with".