Britney Spears is in “serious danger” on both the mental and financial front and is doing way worse than she was under the conservatorship … sources with direct knowledge tell TMZ.

As for her mental health, our sources say Britney is “completely dysfunctional.” Since the conservatorship ended, she has no supervision and, according to sources, has radical mood swings that we’re told are “shocking.”

We’re told she’s almost totally isolated and, as it was put to us, dangerously unstable.

We’re told the few people who remain in Britney’s life say she was doing much better when she was under a conservatorship. As one source said, “She had lots of freedom in the conservatorship and the restrictions were there to protect her. She’s not protected anymore.”

Our Britney sources are angry at what’s happened since the conservatorship ended, saying she’s gotten absolutely “no justice” … and that involves her finances.

We’re told Britney has been spending a fortune and is in real danger of going broke. Our sources say she’s been going to French Polynesia, staying at The Brando, and spending close to a million dollars each trip between private jets, hotels, staff, etc. She goes every month or 2. We’re told she also goes to Hawaii almost monthly by herself, taking a private jet, staying in the Presidential Suite at the Four Seasons, and dropping $350k a trip.

“She cannot afford this. She had $60 million when the conservatorship ended, and she’s now where the conservatorship started — in danger of going broke” … one source said.