Bernard Tomic has denied threatening Lleyton Hewitt and his family, calling Australia's Davis Cup captain a "liar" after Hewitt's extraordinary allegations of physical threats and blackmail on Thursday night.

"I have never threatened his family,” the Herald Sun quoted Tomic as saying on Friday.

“Nice, Lleyton. To think how low of a person you actually [are] and [it’s] why the Australian public never liked you.

“I got nothing to do with your family and I don’t care what’s wrong with you, you liar.”