Ben Affleck -- Threatening Lawsuit Over Nanny Dating Allegations

Ben Affleck is angry over allegations he's dating his children's nanny, so angry he's threatening a lawsuit.

A rep for Affleck calls the US Weekly story -- which claims Affleck and the nanny, Christine Ouzounian, began dating AFTER Ben and Jennifer Garner split but before they announced their divorce -- "complete garbage and full of lies."

The rep adds Affleck is "considering legal options."

Affleck and Garner announced their split last month after ten years of marriage.