MF Global's North America chief financial officer plans to tell lawmakers on Wednesday that she desperately sought fund transfers to cover the customer account shortfall in the final hours before the firm's collapse, but that some banks would not execute them.

In prepared testimony, Christine Serwinski also said she was convinced at first that the roughly $1 billion deficit in customer funds had to be an accounting error and only learned on the morning of the bankruptcy that the shortfall was real.

We worked relentlessly throughout the early morning hours and, indeed, throughout the day on October 31, to try to bring the segregated and secured accounts back to the appropriate levels, she said in her first public remarks about the events surrounding MF Global Holdings Ltd's collapse and the ongoing search for missing customer money.

Although we were able to move some funds into the (futures brokerage's) segregated and secured accounts, a number of submitted transfers were not executed by the banks, and we were unable to move sufficient funds to make up for the shortfall.

The House Financial Services panel hearing on Wednesday will for the first time give lawmakers an opportunity to question a crucial second tier of MF Global executives, the people who had operational control over money transfers at the brokerage.

Top executives, including former chief executive Jon Corzine, have already testified and denied knowledge of any improper transfers.

Serwinski is due to appear alongside General Counsel Laurie Ferber, Chief Financial Officer Henri Steenkamp and Assistant Treasurer Edith O'Brien.

Diane Genova, deputy general counsel for JPMorgan Chase & Co , is due to testify on a second panel.

MF Global filed for bankruptcy on October 31 after investors and customers became rattled over the firm's $6.3 billion bet on European sovereign debt.

While regulators and law enforcement officials continue the search for the missing money, the committee is also conducting its own inquiry, and plans to eventually release a report outlining its findings.

FUND SHORTFALL

In her written testimony, Serwinski said she was on vacation during many of the days leading up to the bankruptcy and only sporadically read emails or spoke to colleagues by telephone.

I was reassured that everything was under control and at no time did anyone ever suggest that I should return to the office, she said.

However, she decided to return from her trip a day early, on Sunday, October 30, after she learned about the efforts to sell a significant portion of MF Global's business and about a deficit in a firm invested amount of funds that were meant to serve as a buffer to protect customer money.

Serwinski said the deficit came about because the securities brokerage unit of the firm had borrowed money from its futures unit and missed the wire deadline to pay it back. But she was assured the money would be returned by the next day.

But in the days that followed, she learned the firm was missing money from its customer accounts.

She returned to work thinking the $1 billion deficit was so large that it could only be the result of an accounting error.

On Monday morning, however, the assistant treasurer handed her a piece of paper that said the shortfall was real and not an accounting error.

At some point during the final hours of the firm's life, the Securities and Exchange Commission expressed concern to MF Global regarding the firm's calculation of excess funds in the broker-dealer customer reserve account and cautioned MF Global against transferring these funds, according to a written summary of the congressional inquiry into the matter. Notwithstanding the SEC's admonition, MF Global transferred the funds.

In her prepared testimony, Serwinski denied knowledge of any such admonition and said that had she been aware of any regulatory concerns, she would not have proceeded with an effort to transfer the funds in question.

BONUS SCRUTINY

In a separate development late on Tuesday, the U.S. Senate unanimously passed a non-binding resolution opposing potential bonuses for MF Global executives.

The resolution, introduced by U.S. Senators Debbie Stabenow, a Democrat from Michigan, and Pat Roberts, a Republican from Kansas, said bonuses should not be paid to executives and employees responsible for day-to-day management and operations until customers' segregated account funds are repaid in full and federal investigations have revealed the cause of and parties responsible for the loss of customer money.

Sources close to the trustee overseeing the bankruptcy of MF Global Holdings Ltd have said he may ask a bankruptcy judge to approve performance-based bonuses to a few top MF Global executives under a retention plan.

Ferber and Steenkamp would potentially receive such payouts.

But Kansas Senator Roberts, in introducing the resolution on Tuesday, said: Any recovered funds should go to customers instead of winding up in the hands of those who mismanaged the funds in the first place.

(Additional reporting by Philip Shishkin and Basil Katz; Editing by Andre Grenon and Edmund Klamann)