Frank DiPascali Jr., a central figure in the Ponzi scheme operated by Bernard L. Madoff, will remain in jail until his sentencing next spring, despite efforts by federal prosecutors to win his temporary release so that he can more easily assist their continuing investigation.

At a hearing Wednesday, Judge Richard J. Sullivan of Federal District Court in Manhattan denied Mr. DiPascali’s second bail request. He has been in jail since Aug. 11, when he admitted helping Mr. Madoff conduct his enormous fraud and pleaded guilty to charges that carry a possible prison term of 125 years.

At that time, prosecutors disclosed that Mr. DiPascali, who oversaw the creation of an elaborate phony paper trail that concealed the fraud for decades, had agreed to cooperate with their investigation in exchange for possible leniency, and they asked that he remain free on bail to facilitate that effort.

Judge Sullivan denied that first request, concluding that the length of Mr. DiPascali’s potential sentence might tempt him to flee before his sentencing hearing next spring.