Lorenzo Lamas -- Shauna Sand is an Unfit Mother Who is All About Sex

Lorenzo Lamas claims his ex-wife is an unfit mother who has sex on the beach in front of photogs, is deep into making sex tapes, and lets strange men live in the home she shares with their daughters.

Lorenzo is in a brutal fight with Shauna Sand over custody of their 3 kids. Lorenzo says Shauna is so irresponsible, she made $250,000 off a sex tape for Vivid and blew the money on a Bentley. He also submitted screen grabs of the porn for good measure.

Lorenzo also included pics of Shauna taking the 3 girls -- now 16, 15 and 13 -- to Mr. Bones Pumpkin Patch in West Hollywood and flashing her goods to the paparazzi.

The "Renegade" actor is especially alarmed because he says Shauna is constantly bringing new men to live with her ... and the various apartments are like revolving doors, endangering the kids.

Lorenzo says, "I only pray that our daughters will not take after their mother and think that posing for the camera nude while performing sexual acts is an acceptable way to earn a living."

The girls all wrote letters to the judge, begging him to give their dad custody.

But 43-year-old Shauna -- who says in the docs she's pregnant -- claims Lorenzo is a hypocrite. When they were married she says he encouraged her to make sex tapes, saying he was down with it as long as it paid the bills.

As for photos of her having sex in public, she denies it was sex, saying, "It was a montage for a French magazine."