Former MF Global Chief Executive Jon Corzine is expected to testify at a congressional hearing next month, a committee aide said on Friday, tamping down speculation that the former head of the bankrupt brokerage would decline to take part.

The House Financial Services Committee announced earlier this week that Corzine, a former U.S. senator and governor of New Jersey and one-time head of Goldman Sachs, would appear at a December 15 investigations subcommittee hearing.

Corzine's attorneys, gave us every indication he was willing to testify under oath, said the staffer, who was not authorized to comment on the record. Unless he has a change of heart at the last minute, we expect him to talk and not take the fifth, he said, referring to the constitutional protection against self-incrimination.

Corzine's attorney, Andrew Levander, was not immediately available to comment.

MF Global filed for bankruptcy on October 31, after $6.3 billion in risky bets on European sovereign debt spooked investors and an effort to sell the firm failed.

Regulators and Justice Department officials have been investigating the firm's sudden demise and seeking the whereabouts of around $1.2 billion in customer funds.

The congressional staffer also confirmed that the big three credit ratings agencies have agreed to testify about their relations with the company prior to its collapse.

Moody's and Fimalac SA's Fitch Ratings did not cut their investment-grade ratings of MF Global until days before it failed. McGraw-Hill Cos' Standard & Poor's only did so after it filed for bankruptcy.

The three agencies were not immediately available for comment.

(Reporting by Alexandra Alper; Editing by Tim Dobbyn)