Perez responded, Tweeting, "Game on!" and linking to a number of past stories of the actress' ups and downs over the last few years.
Lindsay responded by Tweeting links to unflattering photos of Hilton during his heavier days.
"the diary of…. a TRUE mean girl (yet, i coined that title)," she Tweeted, linking to a photo of a more robust Perez in a pink wig.
"some that are as far under as he is, choose not to recognize when enough is enough… DENIAL and INSECURITY should be his blog," she Tweeted later. "it's just a way of entertaining myself.. i'm home and with friends.. it's funny, THIS IS HIS LIFE!-how sad?"
Perez has been an outspoken critic of LiLo in recent weeks on both Twitter and his blog.
"I genuinely wish her well," he recently told Access Hollywood. "I have taken to a public forum to express my desire for her to get better… Lindsay needs help."
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