(Reuters) -A group of Democratic senators called on Wells Fargo to end its alleged campaign against employee unions, saying a more constructive approach could address a toxic workplace culture and help the bank recover from scandals that prevented it from growing.

In a Wednesday letter to Wells Fargo CEO Charlie Scharf, 15 senators led by Arizona's Ruben Gallego said the fourth-largest U.S. bank's history of setting aggressive sales goals led to mistreatment of consumers, staffing shortages and substandard pay, providing an incentive to unionize.

The senators also said Wells Fargo has become "significantly more aggressive" in retaliating against employees who try to organize, including in Arizona, Florida, North Carolina and Wyoming, and that six unfair labor charges have been filed this year with the National Labor Relations Board.

"Your employees are entitled to fair wages and safe working conditions," including freedom to report "problematic policies," the letter said. "We urge you to stop this union busting campaign."

Wells Fargo did not immediately respond to requests for comment.

The Committee for Better Bankers, which is a coalition of bank workers, labor groups and advocacy groups, is assisting with the unionization effort. It also did not immediately respond to requests for comment.

FED NOTED SUBSTANTIAL PROGRESS IN GOVERNANCE

Like many employers, Wells Fargo has had a sometimes fraught relationship with employees.

The San Francisco-based lender became the first big U.S. bank with a union at the end of 2023, a rare moment for an industry that has largely been immune from them.

After becoming enmeshed starting in 2016 in far-ranging scandals where employees opened millions of unauthorized and unnecessary customer accounts, Wells Fargo created a conduct management intake department to address a variety of complaints.

That department and at least 27 branches have voted to unionize.

Wells Fargo ended last year with 217,000 employees, with 77% in the United States.

In June, the Federal Reserve lifted a seven-year-old restriction that capped Wells Fargo's assets at $1.95 trillion, citing the bank's "substantial progress" in addressing deficiencies, and improving governance and risk management.

Wells Fargo awarded nearly all full-time employees $2,000, mainly as restricted stock grants, to recognize the Fed decision and give them a chance to "own a part of Wells Fargo and hopefully benefit from our future success."

Senators who signed Wednesday's letter also included Arizona's Mark Kelly, California's Alex Padilla and Adam Schiff, Connecticut's Richard Blumenthal and Chris Murphy, Illinois' Tammy Duckworth and Richard Durbin, Maryland's Chris Van Hollen, Massachusetts' Elizabeth Warren, Minnesota's Tina Smith, Nevada's Catherine Cortez Masto, New Jersey's Cory Booker, New Mexico's Martin Heinrich and Vermont independent Bernie Sanders.