The Consumer Financial Protection Bureau (CFPB) is unveiling a rule that would restore consumers’ rights to bring class action lawsuits against financial institutions, delivering a blow to Wall Street that could cost the industry billions of dollars. The rule, which would apply to bank accounts, credit cards, and other types of consumer loans, is likely to take effect since it does not require congressional approval.

The new rule means that lenders can not include mandatory arbitration agreements, which bar class actions, in their contracts. The changes would not apply to existing accounts. Alan S. Kaplinsky, a Ballard Spahr partner who pioneered the use of such agreements, testified at the CFPB hearing on the matter. He, and other backers of arbitration, argue that the private legal system is a more efficient way to resolve disputes and class action lawsuits are primarily a boon to plaintiffs’ lawyers.

“It’s going to spell the end of arbitration,” Mr. Kaplinsky said. “It will lead to a huge upsurge in litigation and take away a benefit to consumers.”

The rule also drew opposition from the U.S. Chamber of Commerce and other business groups. “The proposed rule is a wolf in sheep’s clothing,” the Chamber said in a statement. “Now the agency designed to protect consumers is proposing a rule that will end up hurting them.”