“We have too much recent experience with insufficiently regulated financial markets spinning out of control to let this happen again,” the letter concludes. “The Facebook proposal must be put on hold until these numerous and fundamental questions are resolved.”

Other signatories to the letter include Demos, the Economic Policy Institute, the U.S. chapter of Friends of the Earth, Global Witness, the National Consumer Law Center, RootsAction.org, and the Service Employees International Union (SEIU).

The lawmakers addressed in the letter are the tops Republicans and Democrats on the U.S. Senate’s finance and banking committees as well as the U.S. House’s Energy and Commerce, Ways and Means, and Financial Services committees. The regulatory entities named are the U.S. Securities Exchange Commission; U.S. Federal Trade Commission; Office of the United States Trade Representative; U.S. Commodity Futures Trading Commission; Board of Governors of the Federal Reserve System; Financial Stability Oversight Council; and Financial Crimes Enforcement Network.

The progressive organizations behind the new letter are far from alone in sounding the alarm about concerns related to Facebook’s efforts to create a global cryptocurrency—among them, American economist and Columbia University professor Joseph Stiglitz, who charged in a piece for Project Syndicate Tuesday that “only a fool would trust Facebook with his or her financial wellbeing.”

“In just a few short years, Facebook has earned a level of distrust that took the banking sector much longer to achieve,” wrote Stiglitz, who also raised questions about Facebook’s business model for Libra. “Time and again, Facebook’s leaders, faced with a choice between money and honoring their promises, have grabbed the money. And nothing could be more about money than creating a new currency.”

In an article produced by the Independent Media Institute’s Economy for All project and published Sunday by Salon, market analyst Marshall Auerback argued that although U.S. regulators have largely failed to rein in Silicon Valley giants—especially Facebook—when it comes to social media platforms, “it’s hardly likely” that financial regulators around the world will be “pussyfooting” around issues raised by the cryptocurrency project.

“If Facebook introduces a cryptocurrency that in effect seeks to privatize or displace existing central bank functions, it is inevitable that the company will face a ton of regulatory oversight crashing down on it,” Auerback wrote. “Social media might be a newfangled type of business that doesn’t lend itself easily to the regulatory strictures of the Sherman Act, but money is precisely the kind of thing guaranteed to bring the Federal Reserve, the IRS, and several other regulatory bodies crashing down on Facebook, given this systemic risk.”