“Newlyweds” star Nick Lachey has threatened to move out on his ditzy blonde wife, Jessica Simpson, sources told The ENQUIRER.

Friends say the couple are fighting over a myriad of issues: Nick can’t stand Jessica’s meddling family; he’s–say pals ready to have kids, but she isn’t; and he’s jealous of her success, while his career tanks.

Their differences came to a head after Jessica signed a deal for four ABC specials and then won the part of Daisy Duke in the movie version of “The Dukes of Hazzard.” Nick was left out of the ABC deal and failed to land the role of Bo in the movie.

“Jess and Nick had made a pact that neither would do the movie if they both didn’t get roles,” said an insider. “Nick feels Jess is only looking out for herself. He told her: ‘That’s it. I’m movin’ out!’

“Jessica was crying. She didn’t know what to say or do.”

He eventually came back to her, but as their second anniversary approaches on October 26, they continue to fight over fundamental issues, says the insider.

“Jess had promised Nick that they’d start a family this year,” said the insider.

“When he begs her to cut back on work, her answer is that she has to strike while the iron’s hot.

“To Nick, it must seem like Jess can’t keep her word.”

The strain was apparent August 29 while they were in Miami for the MTV Video Music Awards.

During dinner at a posh restaurant called Nobu with Jessica’s parents and pop star sister Ashlee later that evening, Nick disappeared and was eventually spotted with several very attractive women.

“It didn’t take Nick long to find a few gorgeous ladies to hang with.

“He laughed and danced with everyone but his wife,” said the insider.

When Nick and Jessica got back to their hotel room, he exploded, according to a close source. “He told her that he’s sick of her father managing her life, and that he married her, not her family,” said the source.

“Jessica broke down in tears. He left and slammed the door behind him.”

Nick’s publicist denied the couple are having problems, telling The ENQUIRER: “Jessica and Nick are very happy and very much together.”

But the insider added: “Nick and Jessica are both young, beautiful and successful. But Nick is ready to walk!”