8:20 AM PST -- A rep for Dina Lohan tells us Dina has denied selling any of Lindsay's stuff.
Lindsay Lohan's mother is unloading her daughter's prized possessions with an online flea market -- which Lindsay's threatening to shut down with a little help from cops ... TMZ has learned.
Sources close to Lindsay tell us she recently got wind of Dina Lohan's scheme -- selling off Lindsay's clothing, furniture, artwork, etc ... on the Internet and directly to friends ... all without LiLo's permission. We're told she's hawking items from the massive stockpile of stuff Lindsay moved into Dina's house during the Oprah docuseries.
It may seem like a bunch of junk, but Lindsay says it's worth millions. As for Dina's motivation -- we're told she thinks anything left behind in HER garage ... is hers to sell. Linds thinks Dina's just desperate to pay bills.
We broke the story -- Lindsay's already pissed at Dina for negotiating a deal to be on "Celebrity Big Brother UK" ... and our sources say this fire sale might be the last straw.
Lindsay is urgently trying to get friends to go scoop up her loot before it's all gone -- but if that doesn't work ... we're told she'll get police involved.