Sam Fender is the latest artist to announce he will “no longer be working” with promoter SSD Concerts.
He said on social media he was “completely overwhelmed” by stories he had heard from people working there.
A number of anonymous posts on jobs website Glassdoor alleged that management had made sexist comments and mistreated staff.
Managing director Steve Davis has resigned and SSD Concerts said claims would be “investigated thoroughly”.
The ex-boss said he was “truly sorry” that “some people have been upset or made to feel uncomfortable” while working at the company.
Artists such as Idles and Lanterns on the Lake have also said they will not be working with SSD and singer L Devine has pulled out of a festival the company has organised.
Brit Award winner Sam praised SSD workers for coming forward and said it had taken “great courage” for them to share their stories.
Sam, who is from North Shields in Tyne and Wear, added in a statement on Instagram: “The local grassroots scene means so much to me, my band and team. I hope that we can take this opportunity to build a more inclusive industry that is a safe space for all”.
SSD describes itself as one the largest live event promoters in north-east England and put on socially distanced festivals in Newcastle last year, with Sam Fender and The Libertines among the line-up.
But allegations against the company have become the focus in recent weeks after its Instagram account was hacked and used to post screenshots of reviews from angry staff members.
Northumbria Police told the BBC a 25-year-old man was arrested and cautioned for “performing a function that gains unauthorised access to a computer”.
However, the force said it had no records of allegations made by staff about the company.
SSD released a statement last week calling the online claims “malicious” but said it was taking them “seriously”.
On Monday it confirmed the resignation of the firm’s managing director, Steve Davis.
A statement on SSD’s Instagram added that the wellbeing of its staff was “of the utmost importance” and any allegations “should be investigated thoroughly”.
The company added that an outside organisation will look into the allegations.
After the reviews were made public, music development agency Generator said it had heard “exceptionally worrying accounts” from workers.
The PRS Foundation, which helps to fund new artists, added: “Misogyny and abuse is unacceptable”.