David Beckham has been told to "drop his pants in court" by the hooker, who claimed she had a threesome with the footballer, to prove his innocence.
Irma Nici insisted she knew intimate "distinguishing characteristics" which would support her story.
Becks sources branded her a desperate, raving liar, and he has lodged a 16 million pounds writ after the 26-year-old Bosnian hooker challenged him to drop his pants in court to prove his innocence.
Team Beckham lawyers vowed to step up their bid to sue her and the US magazine, which published the vile slur for 16 million pounds damages.
"This should be seen for what it is - the ravings of a desperate woman," the Sun quoted a source as saying.
"She is a malicious fantasist without a single shred of evidence to support her pack of lies.
"The writs stand against her, the magazine and its publishers. The statement is further proof that she has absolutely no evidence.
"If she had, she would have disclosed it by now to one of the many publications she has been trying to hawk her story to. It is not surprising that she's had no takers," the source said.
The source added: "Attention is now being focused on the magazine publishers as to why they maliciously went ahead with this article, knowing it was based on lies."
However, Nici seems unmovable from her words.
Nici's management said earlier: "Irma stands by her previous statements. Any lawsuit against her is a publicity stunt and without merit.
"Any attorney who brings an action against her should be prepared to face sanctions and pay all legal costs because they will lose.
"There is more to the story that Irma hasn't told yet. We are highly confident that Irma can provide enough detail and other forms of proof to persuade a jury that her tryst with David Beckham did indeed take place.
"Mr Beckham had better be prepared to drop his pants in court if he wants to pursue this matter as he has distinguishing characteristics which will prove without a doubt that Irma is telling the truth.
"Mr Beckham's baseless lawsuit is understandable. After all, he has to tell Posh something," the management added.
Becks' 21-page writ was lodged with a Los Angeles court on Friday. It details his claim for around £16million plus punitive damages.
In addition to Nici and US magazine In Touch, which printed the story, the mag's publishers Bauer and its editor Michelle Lee are also named as defendants.
