Heather Mills has threatened to release a tape recording of Sir Paul McCartney and his designer daughter STELLA mocking her for having a prosthetic leg. Mills, who lost her left leg in 1993 when she was hit by a police motorcycle, is alleged to have recorded the telephone conversation between the pair last year (06) after bugging the phone line at the former Beatle's U.K. country estate in Peasmarsh, East Sussex. And when the ex-model confronted MCCartney about the tape, he is said to have apologised immediately. A close friend of Mills tells British newspaper the Sunday Mirror, "What she says she heard Sir Paul say on the tape about her amputated leg left her incandescent with rage. "She says he used an insulting slang word about disabled people. That he and Stella - her arch-enemy - had a laugh about it. Heather was - and still is - seething about it." The tape recording is one of many Mills has vowed to make public if her divorce battle with the singer turns nasty.