A U.S. Senate committee memo said Microsoft Corp. used aggressive international tax maneuvers to avoid billions of dollars in taxes over the past three years.

The committee memo, released for a hearing today in Washington, said Microsoft used transactions with subsidiaries in Puerto Rico, Ireland, Singapore and Bermuda to save at least $6.5 billion in taxes. The committee also revealed that Hewlett- Packard Co. has used a series of short-term internal loans that allowed the company to tap its offshore cash for domestic operations without paying taxes, according to the memo.

Senator Carl Levin, a Michigan Democrat and chairman of the Permanent Subcommittee on Investigations, didn't accuse the companies of acting illegally, though he said he was “highly dubious” that HP was in compliance with the tax law.