In his testimony, Corzine distanced himself from some hands-on aspects of the firm's business practices.
"Even when I was at MF Global, my involvement in the firm's clearing, settlement and payment mechanisms and accounting was limited," Corzine said.
"I was stunned when I was told on Sunday, October 30, 2011, that MF Global could not account for many hundreds of millions of dollars of client money."
He said he accepts responsibility for the repo-to-maturity trades that related to the firm's $6.3 billion bet on European sovereign debt.
"At the time that MF Global entered into the transactions, I believed that its investments in short-term European debt securities were prudent," he said.
However, he said MF Global reduced leverage during his tenure, and that he does "not claim to be an accountant" regarding the treatment of that exposure.
Mary Schapiro, the chairman of the U.S. Securities and Exchange Commission, has said her agency is probing the accounting treatment that helped mask MF Global's exposure to risky foreign sovereign debt. The SEC is also probing the disclosure of that exposure.
Steve Luparello, vice chairman of the Financial Industry Regulatory Authority, said in his testimony on Thursday that MF Global was not fully candid with FINRA in 2010 when the firm was asked about its exposure to European debt.
Luparello said the firm indicated in late September 2010 that it "did not have any such positions" in European sovereign debt.
"We later learned that the firm began entering into transactions that carried European debt exposure in mid-September 2010," he said.
(Reporting by Sarah N. Lynch in Washington and Ann Saphir in Chicago, writing by Karey Wutkowski; editing by John Wallace, Dave Zimmerman)