Lindsay Lohan says there's NO TRUTH to reports she was boozing at a SAG Awards after party this weekend ... and now, TMZ has learned, she's threatening to SUE the media outlets that published the story in the first place.
A source close to the actress tells TMZ ... Lindsay is already exploring her legal options with her attorneys ... because she feels the false stories are sabotaging her effort to save her career.
Lindsay acknowledges she WAS at the party at the Chateau Marmot hotel in Hollywood Sunday night ... but insists she was sitting with Alan Cumming the whole time and ONLY drank water.
We're told Lindsay's also pissed over reports about a recent gas station makeout session with Dennis Hopper's son Henry (pictured above), where she allegedly purchased Red Bull and vodka.
Sources close to LiLo tell us the actress is adamant the two are just friends ... NEVER MADE OUT ... and the only items she bought were soda, chips, and cigarettes.