2020 presidential candidate Michael Bloomberg is receiving heavy criticism for hiring a call center that uses prison labor which can pay as little as $20 a month.

Multibillionaire presidential candidate Michael Bloomberg hired a contractor that used prison labor to make phone calls for his White House bid, the Intercept reported on Tuesday, bringing further controversy to a long-shot presidential bid that has already faced criticism for the candidate’s improper use of his personal fortune to influence the democratic contest.

“According to a source, who asked for anonymity for fear of retribution, people incarcerated at the Dr. Eddie Warrior Correctional Center, a minimum-security women’s prison with a capacity of more than 900, were making calls to California on behalf of Bloomberg,” wrote the Intercept’s John Washington. “The people were required to end their calls by disclosing that the calls were paid for by the Bloomberg campaign. They did not disclose, however, that they were calling from behind bars.”

Bloomberg’s campaign canceled its relationship with the contractor on Monday after being questioned by the Intercept: “We didn’t know about this and we never would have allowed it if we had,” Bloomberg spokesperson Julie Wood told the Intercept. “We don’t believe in this practice and we’ve now ended our relationship with the subcontractor in question.”

Prison labor has been widely criticized as modern slavery, as incarcerated people are forced to work for private corporations for little or no pay and punished if they refuse.

“The Department of Corrections website lists the maximum monthly wage for the incarcerated at $20 dollars a month, but another policy document says there is a maximum pay of $27.09 per month,” reported the Intercept. The co-founder of ProCom, the call-center company contracted by Bloomberg’s campaign, assured the Intercept that its incarcerated workers make significantly higher wages, insisting that “some of them are making that much every day.” The Department of Corrections did not respond to the Intercept’s requests to clarify the discrepancy.

“Step 1: Billionaire uses unconstitutional policing policies to imprison tons of poor people,” tweeted Politico writer Jonathan Topaz, referring to Bloomberg’s stop-and-frisk policy as New York City Mayor. “Step 2: Same billionaire uses prison labor for his presidential campaign.”

Critcs argued that Bloomberg, who has poured millions into his campaign, should have done a better job vetting his contractors and making sure his staff made a living wage.

“When you have so few organic supporters that you need to use slave labor to phone bank,” tweeted progressive non-profit the Gravel Institute, mocking Bloomberg’s low poll numbers.

“It’s entirely possible they didn’t know,” Alex Friedman, managing editor of Prison Legal News and an advocate for incarcerated people’s rights, told the Intercept. “But that’s like saying department stores making clothes in southeast Asia don’t know that 5-year-olds are stitching together their soccer balls. Well, shouldn’t you know? Shouldn’t you have some idea of your supply stream, or what your downside supply stream is doing?”

Bloomberg’s Fortune

The episode is not alone among controversies that have ailed the former New York City Mayor’s late entry into the presidential election. At an estimated net worth of $54 billion, Bloomberg is the richest candidate in the race. He has taken advantage of his fortune by spending over $76 million in television advertisements and is estimated to potentially spend billions more, drawing criticism for tainting the democratic process with his enormous wealth.

As CNBC reported, some of Bloomberg’s millions are going into a secretive tech firm he founded months ago. The firm, called Hawkfish, will be a “primary digital agency and technology services provider for the campaign,” Julie Wood, a Bloomberg campaign spokeswoman, told CNBC.

The multi-billionaire candidate’s ownership of financial information and media company Bloomberg News is also a subject of ethics concerns. Although the outlet pledged to refrain from investigating other candidates during the primary, Bloomberg published a story on Monday criticizing Sanders and Warren’s campaigns for spending money at Amazon despite pressuring the tech giant to pay federal taxes and improve conditions for workers.

“So it may surprise voters to learn that the eight leading Democratic candidates and Trump have spent almost $600,000 on Amazon in the first nine months of 2019, mostly for office supplies, according to federal campaign records,” wrote Bloomberg’s Spencer Soper. “The stridency of the anti-Amazon rhetoric tends to correlate with the size of the outlay on its website.”

Critics quickly lambasted Soper’s piece for infringing on Bloomberg’s pledge.

“Hit pieces on progressive candidates become questionable when run by a news outlet owned by one of their rivals,” tweeted David Dayen, executive editor at The American Prospect. “This as much as anything shows why Bloomberg must sell Bloomberg News, the inability to do so is debilitating to democracy and a free press.”

As Common Dreams reported, Bloomberg’s premise was broadly mocked as absurd:

“Sanders and Warren have aggressive plans to cut back on carbon emissions, yet they both inhale oxygen and exhale carbon dioxide,” tweeted Leah Greenberg.

“Warren, Sanders demand stronger clean-water regulations, but their campaign staff have taken thousands of individual showers in it and used it for hundreds of thousands of brushstrokes of teeth,” tweeted Joe Rospars.