While President Joe Biden’s tax and spending policies have made a mess of the economy , his federal regulators have been aggressively pushing an extreme agenda that would harm the economy even more.

Chief among them is Federal Trade Commission Chairwoman Lina Khan , who has launched so many assaults against companies and the private sector that former Treasury Secretary Larry Summers has said it seems “almost like a war on business.”

Her string of high-profile lawsuits, court losses, and new merger guidelines are getting all the attention. But a little-noticed rule the FTC recently proposed is just as harmful: amendments to the Hart-Scott-Rodino antitrust law that would have far-reaching negative effects on the economy.

The FTC has proposed a fundamental and radical overhaul of the HSR premerger notification rules, drastically expanding the rules companies have been operating under for more than 45 years. Under the existing rules, more than 98% of premerger notifications are approved without a second question. Fewer than 2% are required to provide more information.

But under the proposed amendments, every single transaction, 100% of them, would be subject to new and greatly enhanced filing requirements and the same level of scrutiny now applied to only 2% of transactions. It is like the FTC wants to block every merger and acquisition.

The new rule would be enormously costly and burdensome, forcing companies to spend hundreds of hours collecting and submitting data, some going back 10 years. A U.S. Chamber of Commerce study found the filing burden would be five times greater than the FTC has estimated and would cost filers more than $2 billion a year.

The new rule would be especially costly and invasive to small and midsize firms. While big corporations could afford the added compliance costs and legal challenges, government regulators would be in a position to bully smaller companies and block them from expanding to survive.

The new rule is so far-reaching it would turn the FTC into a massive data collection agency of private companies with none of the safeguards required of the IRS.

Not surprisingly, private sector opposition to the proposal is growing. Manufacturers, retailers, and small businesses have all expressed concerns about the proposal’s potential negative effects on consumers and businesses.

The National Association of Manufacturers said it “would result in significant costs and delays for manufacturers.” It would also have “a chilling effect on investment,” according to NAM President and CEO Jay Timmons.

The National Retail Federation said the rule would “impose substantial additional costs on merging parties,” imposing an enormous burden on the industry that supports 1 in 4 jobs.

The Chamber of Commerce said the proposal would “damage investment and capital flows, harming the U.S. economy, including workers and consumers.”

As these comments show, the new FTC rule would strangle the ability of small and midsize firms to expand, create new jobs, and provide better wages and benefits to their employees. It would discourage private investment and innovation and reduce the long-term growth of the U.S. economy. The economic costs of this extreme rule would be staggering, and the FTC should withdraw it.

Bruce Thompson was a U.S. Senate aide, assistant secretary of Treasury for legislative affairs, and the director of government relations for Merrill Lynch for 22 years.