Michael Douglas' Ex-Wife -- My Lady Junk Was Clean as a Whistle

Michael Douglas' ex-wife wants to make something perfectly clear -- eating out was safe when he was married to her.

Douglas told a British paper over the weekend ... his 2010 throat cancer was "caused by HPV [human papillomavirus], which actually comes about from cunnilingus."

Diandra Douglas -- whose epic divorce from Michael in 2000 was one of the richest marital settlements in history -- tells TMZ she does NOT have HPV ... period.