The Treasury Department took aim on Monday at a rule that would allow millions of Americans to band together in class action lawsuits against Wall Street firms, saying it could trigger frivolous lawsuits and drive up the cost of credit.

In an 18-page report, the department said the Consumer Financial Protection Bureau, which adopted the rule this summer, did not adequately evaluate the harm it could cause to consumers.

The report arrived amid a broader push by the Trump administration to relax or repeal regulations, including those that affect financial institutions. Treasury has published two reports recommending a series of changes to financial rules put in place after the 2008 financial crisis.

The arbitration rule, which is set to take effect in 2019, will prevent credit card companies and other financial institutions from using the fine print of contracts to ban class action lawsuits or force consumers into arbitration, a private system where an individual has to go up alone against a deep-pocketed corporation.