SAN FRANCISCO — Lawyers representing aggrieved customers suing Wells Fargo have said the bank may have opened about 3.5 million unauthorized accounts, far more than bank and regulators disclosed last year.

In a court filing late Thursday, lawyers representing customers told a federal judge in San Francisco that they believe bank workers created the unauthorized accounts over the last 15 years, “based on public information, negotiations, and confirmatory discovery.” The bank initially estimated about 2 million unauthorized accounts were opened dating back to 2009. Last month, the bank said the problem dates back to 2002.

Bank spokesman Ruben Pulido said Friday that the lawyers’ claim was an unverified estimate. “The unauthorized account numbers reported in the filing are estimates made by plaintiffs’ attorneys based on a hypothetical scenario and have not been verified,” Pulido said. “The number of unauthorized accounts estimated in the filing do not reflect actual unauthorized accounts.”

Pulido declined further comment and said the bank has not disclosed its own revised estimate of how many unauthorized accounts were opened.

In September, Wells Fargo agreed to pay a combined $185 million fine to the federal Consumer Financial Protection Bureau and the federal Office of the Comptroller of the Currency and the Los Angeles city attorney.