Allred to David Boreanaz: Pay Up or Else!

5/3/2010 8:00 PM PDT

Gloria Allred to David Boreanaz: Pay Up or Else!

David Boreanaz went public today with his extra-marital affair after Gloria Allred contacted Boreanaz' lawyer and demanded six figures ... sources tell TMZ.

David admitted to PEOPLE mag he had a relationship with a woman -- NOT RACHEL UCHITEL -- but "She asked for money.  I felt as though I was being blackmailed...."

TMZ knows what went down.  We're told Boreanaz had a short-term relationship with the woman -- one source says they hooked up "2 or 3 times."  Sources say he started paying her money -- several thousand dollars here and there -- but she began demanding more, threatening to go public with the affair.  Boreanaz then confessed the affair to Jaime Bergman, his wife of 9 years.

Enter Gloria Allred, who reps the mistress.  Allred contacted Boreanaz' lawyer -- legal pit bull Marty Singer -- and demanded 6 figures.

Boreanaz then blunted the attack by going public with his affair.  He has refused to pay the mistress another cent.

UPDATE:  Gloria Allred just told TMZ what we told you yesterday ... Rachel Uchitel was not the woman who tried getting $$$ out of Boreanaz.