JESSICA SIMPSON and Eric John­son aren’t even married yet, but he’s already fed up with his meddling soon-to-be mother-in-law!

Ever since Jessica gave birth to adorable daughter Max­well on May 1, her mother Tina has become a regu­lar fixture at the couple’s Beverly Hills home – and she’s driving Eric crazy, say sources.

At first Tina would drop by to help out with baby duties and household chores, “which was great because Jess and Eric were so overwhelmed,” said a source. “But then she start­ed spending the night.

“The next thing Jess and Eric knew, Tina had moved into one of the guest rooms with sev­eral suitcases and was staying over a couple of nights a week!”

Tina has time on her hands these days because she recently split from Jess’ dad, Joe, after 34 years of marriage.

According to the source, Tina needles football-player – turned – businessman Eric about how messy he is and accuses him of sabotaging the weight-loss efforts of Jess, 32, who is the new spokesperson for Weight Watchers.

“Eric buys junk food for himself and keeps it in a special cabinet that’s off-limits to Jess because it helps her re­sist temptation,” explained the source. “But without Eric’s permission, Tina threw out his secret stash of food.

“When Eric asked where it went, Tina chastised him for tempting Jess into falling off her diet.”

Now Eric is saying that either Tina goes or he does!

“Jess feels guilty turning her mother out when her mom is dealing with the collapse of her marriage,” added the source. “She promised Eric that Tina’s constant presence is just a temporary thing.

“But if something doesn’t change soon, it’s going to throw a monkey wrench into Jess and Eric’s wedding plans.”