Jessica Simpson Warns Britney Spears About Over-Spending Amid Financial Issues

Jessica Simpson has issued a warning to Britney Spears about her finances ... telling the pop star to be wary of lavish vacays, 'cause it's a real easy way to blow your cash!!!

The singer shared this word of advice while leaving LAX Tuesday ... this while chatting with a pap who was asking her about this topic -- namely, the fact Britney's finances are in disarray.

Watch ... Jessica acknowledges that she takes a lot of lavish vacays herself, which can get pricey fast -- unless you got a Mama Bear who's willing to help out at times, and it sounds like Jessica does. Anyway, they eventually land on Britney herself ... and JS has thoughts.

When she's presented with our reporting that Britney's spending way more than she's making these days -- especially when she's jet-setting -- Jess confesses ... first-rate getaways can certainly burn a hole in people's pockets, especially if you're not careful.

Remember ... we're hearing from our sources that Britney is being anything but careful -- so Jessica's words here absolutely apply -- but with that said, she also offers Brit some grace.

While these trips can be expensive ... she jokingly says they're always worth the memories.

Like we first told you ... the pop princess is at major risk of going broke, spending huge amounts of money on frequent getaways to French Polynesia and Hawaii. We're told Brit regularly flies private and doles out hundreds of thousands for her accommodations.

Hollywood psychiatrist Dr. Charles Sophy even expressed concern for Britney's well-being... suggesting the artist needs medication and perhaps even a new conservatorship to keep her in check.