The U.S. Securities and Exchange Commission is demanding that Galleon hedge fund founder Raj Rajaratnam and others accused of insider trading hand over recordings of wiretap evidence, but the defendants have refused to give them up.

In a flurry of letters made public on Monday in the high-profile Manhattan federal court case involving employees of some of America's best-known companies, Rajaratnam and his co-accused argue that the recorded conversations belong only in a parallel criminal investigation.

U.S. District Court Judge Jed Rakoff also heard oral arguments on the wiretap issue on Monday, but he reserved publishing any ruling until next week.

Separately, Rakoff ruled from the bench that the SEC may file an amended complaint to add new civil charges against Rajaratnam. The request stemmed from a guilty plea on criminal charges by former McKinsey & Co management consultants director Anil Kumar on January 7 in which he said Rajaratnam paid him $1.75 million (1.08 million pounds) in exchange for tips on McKinsey clients.