Ariel Winter's mother recently attempted to leak nude photos of Ariel's sister Shanelle Gray through a Hollywood publicist -- this according to the publicist himself, who could end up playing a critical role in the battle for custody of Ariel.
Jonathan Hay tells TMZ ... Chrystal Workman -- the "Modern Family" star's mother -- contacted him this week, and said she had nude photos of Shanelle she wanted to secretly release to the public.
Hay claims Chrystal hounded him all week about leaking the pics -- which he says are 8 or 9 years old -- but he refused because he felt like Chrystal was trying to "sell out her daughter" ... and he wanted to help Ariel.
Hay says he's already been contacted by a member of Ariel's legal team -- but adds at this point it's unclear how much of a role, if any, he will play in the case.
Hay says he would have no problem filing a declaration in support of Ariel -- but says he has not been asked to do so yet.
Ariel's case will be back in court on December 10.