Kim Kardashian -- Threatens to Sue Over Intrusive 'Naked Photo'

Kim Kardashian is enraged that a photo agency is hawking pictures it claims to show her lying naked at her pool, and she's threatened to haul their asses into court.

Kim's lawyer, Marty Singer, fired off a letter to X17, an L.A. paparazzi agency, claiming the company is hawking pics that were taken in a helicopter hovering over Kim's Hidden Hills home. Singer claims the photog broke the law by taking the pic in a chopper with a telephoto lens.

Singer says even worse ... X17 is lying when it claims Kim was naked. He says she was wearing a blue bikini and when she saw the helicopter she grabbed a towel to cover up.

Singer warned X17 if they sell the pics, they will face big damages for invasion of privacy.

Singer may have gotten through to the agency ... they took the pics off the website.