Federal prosecutors said they plan to introduce audiotape evidence at next week's trial of Raj Rajaratnam showing that the Galleon Group founder conspired with former Goldman Sachs Group Inc director Rajat Gupta to get inside tips about the Wall Street bank.

Assistant Attorney Jonathan Streeter at a Friday court hearing said the evidence concerns the $5 billion investment in September 2008 by Warren Buffett's Berkshire Hathaway Inc into Goldman, as well as Goldman's financial results.

The Berkshire stake remains widely seen as having provided stability for Goldman at the height of the financial crisis.

Rajaratnam's insider trading trial starts on March 8.

(Reporting by Grant McCool, editing by Gerald E. McCormick)