Tan, who jumped bail to seek asylum in the United States, made the allegation in a Facebook posting on Thursday.
Lee has since hit out at him over the allegations and replied with a scathing response titled "Dear Alvin Tan the Almighty", stating that it was her "final act of love" as his allegation was "the last straw".
Facebook user Ivy Lam urged Lee to stop wasting her time by trying to get back Tan’s attention.
Joyce Teo also urged Lee to move on with her life and learn from her mistakes.
"Dear Vivian, just move on with your life and learn from your mistakes. Don't let others take advantage of you," commented Joyce.
"Alvin doesn't deserve to talk about love. Even if she did that, as a friend or an ex-boyfriend, shouldn't you just guide her or care about her? If this is the way you want to show your concern, which is to humiliate her on Facebook, that’s pretty shameful," said netizen Ng Yang Yang.
Adonis Plutus Alangre said advised Tan to be careful in the near future.
"Alvin, karma will eventually catch up with you and hopefully it involves some bizarre accident. You don't actually use your brain that much so it's considered as a waste of oxygen for the rest of us," Alangre wrote.
Ooi Keat Shang said that Tan was just bored in the United States and seeking attention with his Facebook post.
“Hides in the United States and he keeps posting updates on Facebook. He is afraid that Malaysia will forget him. Let him 'enjoy' his freedom alone in the United States,” said Shang.
Yakvb Tvfail felt Alvin was displaying a pattern of chronic narcissistic behaviour and urged him to seek professional help.
Adrian Amalraj said that he has never seen such a “crap” person in his life.
“In my opinion, he should protect and secure the girl he once loved even if they are separated,” said Amalraj.
Tan and Lee were slapped with multiple charges over their now-defunct Sumptuous Erotica sex blog and their controversial "Ramadan greeting" involving a pork dish bah kut teh.
They regained temporary possession of their passports on May 18, but only Lee showed up on June 3 to return it.
The Sessions Court has issued a warrant of arrest for Tan and forfeited his RM20,000 bail after he failed to return his passport on Aug 22.