SACRAMENTO — California’s treasurer is suspending some of the state’s most profitable lines of business with Wells Fargo amid allegations bank employees opened millions of accounts without customers’ permission.

The announcement by the nation’s largest issuer of municipal debt reflects the growing political pressure on the banking giant since it agreed to pay $185 million to settle the allegations. While the sanctions apply to only a portion of California’s business with Wells Fargo, the impact could grow if more states follow suit, as state Treasurer John Chiang urged them to do.

‘‘I have a responsibility to take action aimed at helping Wells Fargo and all financial institutions to understand that integrity and trust matter,’’ said Chiang, a Democrat, who is in a crowded field of Democrats running for governor in 2018.

Chiang said he wants to send a message that the bank’s behavior was ‘‘a legal and ethical outrage.’’

For the next year, Chiang said, he will stop using Wells Fargo as the managing underwriter on negotiated bond sales. In 2015, the bank managed approximately $700 million of bond sales of the type that will be suspended.

The treasurer said his office, which oversees a $75 billion investment fund, will not buy additional Wells Fargo stock and won’t use the bank as a broker for investment purchases. The sanctions will last 12 months.

Chiang said chief executive and chairman John Stumpf should resign, and the board should separate the chairman and chief executive positions.

Spokeswoman Jennifer Dunn said Wells Fargo understands the concerns raised over its sales practices and is working to rebuild trust with customers.

‘‘Our highly experienced and proven government banking, securities, and treasury management teams stand ready to continue delivering outstanding service to the state,’’ Dunn said.

The company said Tuesday that Stumpf and the executive who ran the bank’s retail banking division will forfeit tens of millions of dollars in pay.

Meanwhile Stumpf is scheduled to appear Thursday before the House Financial Services Committee to explain the bank’s response to the crisis. A week ago he appeared before a panel of US Senators, where Democrat Elizabeth Warren of Massachusetts accused Stumpf of “gutless leadership’’ and called on him to resign.