Citing Wells Fargo’s “venal abuse of its customers,” the California treasurer took the unusual step on Wednesday of suspending many of its ties with the San Francisco bank as it continues to reel from the scandal over the creation of as many as two million unauthorized bank and credit card accounts.

The state treasurer, John Chiang, said he was suspending Wells Fargo’s “most highly profitable business relationships” with the state for at least a year, including the lucrative business of underwriting certain California municipal bonds.

On Tuesday alone, he said, he had pulled Wells Fargo off two large municipal bond deals.

“How can I continue to entrust the public’s money to an organization which has shown such little regard for the legions of Californians who placed their financial well-being in its care?” Mr. Chiang wrote in a letter on Wednesday to the bank’s chairman and chief executive, John G. Stumpf, and the bank’s board members.

Mr. Chiang said he was also suspending making any additional investments in Wells Fargo securities and would suspend the bank’s work as a broker-dealer hired to buy investments on the treasurer’s behalf.