The 70-year-old, who is accused of 11 counts of indecent assault against seven girls and women, told London's Southwark Crown Court that the women who claim he indecently assaulted them are telling a "pack of lies".
Mr Clifford made the claims as he was cross-examined by prosecutor Rosina Cottage, QC, on his third day in the witness box.
In an occasionally heated exchange, the veteran celebrity agent was asked to explain why a group of women from different areas, and of different ages and backgrounds, would have made claims about him allegedly assaulting them, sometimes in apparently similar ways.
Ms Cottage asked: "Do you know any reason why these women would have lied to their family and friends all of these years ago?"
Mr Clifford replied: "I don't know, because I don't know them. I know that what they are saying is untrue. I can only think it's because of an opportunity for compensation, an opportunity to make something out of this in the current climate."
He added: "Possibly they are just fantasists, possibly because they don't like me, they see an opportunity - they would be the reasons.
"I know that what they are saying is totally untrue. It's pure speculation for me or anyone else as to why they are doing it. I know it's not true."
Addressing an allegation that he assaulted a girl in his office, Mr Clifford again denied the claim, saying the girl had never worked in his office.
He told the court: "When the [Jimmy] Savile scandal broke we had dozens of women phoning us with stories about Savile, some of whom were obviously lying, and all of whom wanted money."
Mr Clifford denies all charges against him.
The trial was adjourned until Monday morning.