Mitt Romney LIED under oath when he testified in the divorce of his good friend and screwed the friend's wife out of a lot of money in the process ... so claims the ex-wife of Staples' founder Tom Stemberg. Multiple sources connected with the divorce tell TMZ ... during Tom's uber nasty divorce case with ex-wife Maureen, Mitt Romney gave a deposition and testified during the trial that Staples was worth virtually nothing. Romney testified that the company was worth very little and Tom was a dreamer and "the dream continues." Romney characterized the Staples stock as "overvalued," adding, "I didn't place a great deal of credibility in the forecast of the company's future."Partly as a result of Romney's testimony, Maureen got relatively little in the divorce, but we're told just weeks after the divorce ended, Romney and Tom went to Goldman Sachs and cashed in THEIR stock for a fortune. Short story -- Romney allegedly lied to help his friend and screw the friend's wife over.Do you think this will have any legs? Romney's lawyer tells TIME: "This is a decades-old divorce case in which Mitt Romney provided testimony as to the value of a company. He has no objection to letting the public see that testimony."