Kaya Jones, who left the band before they became famous, claimed that she and other members were regularly subjected to sexual abuse.
"We are all abused," she said on Twitter, claiming the group were made to "sleep with whoever they say".
The band, led by Nicole Scherzinger, said they "were not aware of Kaya's experiences" and offered her support.
However, they firmly denied that the remaining members had been abused.
"We cannot stand behind false allegations towards other group members partaking in activities that simply did not take place," they said.
"To liken our professional roles in The Pussycat Dolls to a prostitution ring not only undermines everything we worked hard to achieve for all those years but also takes the spotlight off the millions of victims who are speaking up and being heard loud and clear around the world," the statement continued.
"We stand in solidarity with all women who have bravely spoken publicly of their horrific experiences of abuse, harassment and exploitation."
In their statement, The Pussycat Dolls said: "While we were not aware of Kaya's experiences that allegedly took place during her short time working with us, before the group signed a recording contract, we can firmly testify that we were not privy to any misconduct taking place around us.
"If Kaya experienced something we are unaware of then we fully encourage her to get the help she needs and are here to support her."
'Don't discredit the victim'
The Pussycat Dolls were founded by choreographer Robin Antin in 1995 as a burlesque dance troupe. Their shows attracted a huge following in Hollywood, with stars like Britney Spears, Pink and Brittany Murphy joining them on stage.
In 2003, Antin decided to reinvent the troupe as a pop group, and held open auditions to find new singers and dancers.
Kaya Jones joined the band at this point, but had left by the time they released their debut single, Don't Cha, in 2005 and does not appear on any of their recorded output.
Speaking to The Blast on Monday, Antin called Jones's accusations "disgusting, ridiculous lies" and claimed the singer was "clearly looking for her 15 minutes".
Jones responded by warning the media not to "discredit the victim" by reporting Antin's denials, describing her as a "predator".
"You don't have to believe me," she added. "I lived it.
"It's now about helping other people in the world scared to stand up to their abusers."
Photo copyright: GETTY IMAGES (Caption: The Pussycat Dolls have recently reformed, after a break of seven years)