Sen. Bob Hertzberg took an unusual step shortly after being elected to the California Senate in November, announcing he would moonlight as an attorney at a Los Angeles law firm while serving as a full-time legislator.

Now a consumer group is demanding that Hertzberg disclose the clients he represents at the Glaser Weil law firm, saying the information is necessary to assure the public he is avoiding potential conflicts of interest. Hertzberg, a Los Angeles Democrat, recently introduced legislation to overhaul California’s tax system, a proposal that could impact numerous industries in the state.

“Particularly in light of his new job as chair of the governance and finance committee and his tax reform proposal, we think it’s imperative that he disclose who his clients are,” said Carmen Balber, executive director of Consumer Watchdog, which sent Hertzberg a letter Monday calling on him to report his client list.

“He has said time and again he won’t come close to the line but I think in order for the public to know that’s true we need to know who his clients are.”

Although public officials file annual financial disclosure statements, Hertzberg’s reported income from the law firm would not let the public know which clients he represents, Balber said. Her letter said the Glaser Weil law firm represents several major companies with a financial interest in the decisions that are made in the Capitol, including MGM Grand, Occidental Petroleum, Bank of America and Southern California Gas Company.

Hertzberg’s most recent disclosure report states that he earned more than $100,000 as a partner in the Mayer Brown law firm in 2013, but does not list specific clients. Hertzberg’s next statement, covering his 2014 work for the Glazer Weil firm, will become public in March.

“It doesn’t follow the spirit of the law to name the law firm and not disclose who’s really paying for that salary,” Balber said.

Hertzberg said he has every intention of publicly reporting his clients and agrees that “it’s the right and appropriate thing to do.” He said his legal practice will not conflict with his duties as a legislator because he will likely represent entities outside of California. But so far, he said, “no one has hired me.”

“I don’t have any clients,” Hertzberg said. “But I will disclose when I get them.”