Harry Markopolos, a former financial executive who tried to expose the alleged swindler Bernard Madoff, will tell lawmakers he feared for the safety of his family when U.S. securities regulators ignored evidence in the case, according to a prepared testimony that has been leaked.

Markopolos, will testify that Madoff was one of the most powerful men on Wall Street and in a position to easily end our careers or worse, and that his fund posed great danger to those who investigated it, according to a copy of Markopolos' testimony, which was posted on the Wall Street Journal's website.

Markopolos is scheduled to testify on Wednesday at a House Financial Services subcommittee hearing that is examining how to reform U.S. financial services regulation and better police the markets.

Because nothing was done, I became fearful for the safety of my family until the SEC finally acknowledged, after Madoff had been arrested, that it had received credible evidence of Madoff's Ponzi scheme several years earlier, the testimony said.

Madoff and Markopolos were Wall Street competitors when Markopolos was the former chief investment officer of Rampart Investment Management.

Markopolos said he began looking at Madoff in 1996 after his boss at Rampart asked him to come up with a plan to meet the returns of Madoff's firm.