Mason City, Iowa -- Sen. Elizabeth Warren is challenging Mike Bloomberg's refusal to release from confidentiality agreements women who've worked at his company in what some have alleged are hostile work environments.
Warren on Saturday night questioned the former New York City mayor's claims of championing female employees and criticized his lack of transparency.
"If his company has an enviable record, then let people in his company or former people from his company speak about that enviable record," Warren told ABC News. "What is it that Michael Bloomberg has to hide?"
Her remarks escalated the war of words between Warren and Bloomberg, and come on the heels of Bloomberg's terse reply to Warren's criticisms, as the former mayor told ABC News on Wednesday: "Maybe the senator should worry about herself, and I'll worry about myself."
Bloomberg has continually pointed to his company's "enviable record" on gender parity and has said in answering ABC News’ questions on the issue of harassment culture in his workplace that he champions his employees' success, no matter their sex or race.
Bloomberg on Wednesday told ABC News he wouldn't allow former employees to violate secrecy agreements.
"You can't just walk away from it," Bloomberg said. "They're legal agreements, and for all I know the other side wouldn't want to get out of it. I'm very proud of the ways our company behaves."
"We can always do better," Bloomberg continued. "But we keep looking for better ways to make our employees get better benefits because that's the way you attract good people, and I can parade out a whole bunch of any group that you want that will tell you it's a great place to work."
Last month, ABC News reported on several lawsuits in which Bloomberg was accused of making crude remarks in the 1990s and of allegedly fostering an uncomfortable environment for women to work. Three cases against the company remain active.
Bloomberg has denied the allegations.
After he made those remarks, Warren responded almost immediately.
"When women raise concerns like this, we have to pay attention," the senator said. "We have to listen to them, and if Michael Bloomberg has made comments like this, then he has to answer for them."
ABC News has spoken to several women who've expressed interest in telling their stories who signed confidentiality agreements, but they said they feared possible retribution should they speak out.
Since the outset of his 11th-hour bid for the White House, Bloomberg has pointed to his self-made business success, drawing on that record to build his 2020 platform. However common, nondisclosure deals can become a double-edged sword -- views are mixed on whether such confidentiality protects the accuser -- or helps to silence them -- and in the wake of the #MeToo movement, critics have called for the opportunity for victims to share their stories.
ABC News' Matthew Mosk, Tonya Simpson and Cheyenne Haslett contributed to this report.