"We can't have the subjects of an investigation telling the attorney general who he can subpoena," Corngold said.
The ongoing wrangle over the disclosure of bonus information is the hot button issue as investigators probe if Merrill Lynch or Bank of America, or either firm's employees, violated securities laws when bonuses were doled out.
Merrill's bonuses were historically paid following the close of the calendar year, but the 2008 bonuses were paid in December, just weeks before the merger was finalized, and in a year the firm lost almost $28 billion.
Despite the poor performance of the firm, 696 Merrill employees received bonuses of more than $1 million. Four top employees were given bonuses totaling $121 million.
Cuomo's office is seeking to determine if any laws were violated in the way bonuses were paid on an accelerated schedule by a team that included former Merrill CEO John Thain and Bank of America officials.
Thain had to be served two subpoenas before he answered any questions on the bonuses. During his first deposition, he cited direction from Bank of America as the reason he would not answer. A judge ordered him to testify and said the information would remain confidential until Wednesday's ruling.
Earlier this month, Thain testified before Cuomo's investigators and told him what he knew about bonus recipients and the amounts they netted. But Cuomo's probers want to complete that list – and get as much information as they can on at least the top 200 earners at the firm.