Nick Lachey Raises Questions on Whether He Leaked Story About Awkward Run-in With Ex Jessica Simpson

Pop princess Jessica Simpson is ready to wage war on ex-husband No. 1, Nick Lachey, if he doesn’t stop blabbing about her, insiders say.

Last month on Watch What Happens Live, the 98 Degrees heartthrob told all about a March 29 run-in with the fashion diva during a six-hour flight — even dishing that she parked her three young kids in coach while she relaxed in first class!

“The seating arrangements aren’t that deep or scandalous but somehow Nick is seeing fit to comment,” huffs a Simpson source. “For Jessica, it feels like he’s trying to use this for a hit of fame, riding the coattails of a marriage that ended 20 years ago.”

Citing irreconcilable differences, Nick, 52, and Jessica, 45, split in 2005 before finalizing their divorce the following year.

Page Six reported on the former Newlyweds costars’ mile-high encounter in April, with the Love Is Blind host later detailing how the Irresistible songbird and her mom, Tina Ann Drew, traveled in the lap of luxury as estranged husband Eric Johnson babysat their children — Maxwell, 14, Ace, 12, and Birdie, 7 — back in economy.

Now, insiders warn the Perfect Match emcee better zip it or risk Jess unleashing on him.

“Based on the way Nick reveled in the attention the story brought him, it’s hard not to suspect he may have been the one to leak it in the first place,” adds the insider. “It’s aggravating.”

His loose lips have even forced Jess to publicly defend her parenting — though she pinned the blame on Tina, insisting her mother bought the plane tickets, during a chat with TMZ.

But in truth, “Jessica has no shame over letting her kids fly coach,” spills the insider. “They have done nothing to warrant first class.”