Britain's Daily Mail newspaper on Wednesday reported details of an alleged court document filed by Mills McCartney containing accounts of mistreatment and drug use during the couple's four-year marriage.
"Our client will be defending these allegations vigorously and appropriately," law firm Payne Hicks Beach said in a statement.
The 64-year-old rocker and 38-year-old anti-land mine campaigner announced their separation in May and have begun divorce proceedings in an increasingly acrimonious split. They have a 3-year-old daughter, Beatrice.
The Daily Mail published extracts of what it said was a court document filed by Mills McCartney in response to the former Beatle's divorce petition, lodged in July.
The alleged document claims the former Beatle once attacked his wife with a broken wine glass, stabbing her in the arm and causing profuse bleeding. It also claims that he used illegal drugs and drank to excess.
Mills McCartney's spokesman, Phil Hall, described the divorce proceedings as "highly confidential" and said he could not confirm whether the document was genuine. He said Mills McCartney had been "shocked" by the Daily Mail's report.
Mishcon de Reya, the law firm representing Mills McCartney in the divorce, said it would not comment on "leaked or allegedly leaked documents."
Paul McCartney's law firm said the musician "would very much like to respond in public and in detail to the allegations made recently against him by his wife and published in the press but he recognizes, on advice, that the only correct forum for his response to the allegations made against him is in the current divorce proceedings."
"Our client is saddened by the breakdown of his marriage and requests that his family is allowed to conduct their personal affairs out of the media spotlight for the sake of everybody involved," the statement added.