Fiona Apple -- I REALLY Regret My Weed Arrest

Fiona Apple desperately regrets her hash and weed arrest last week -- because the drug bust is taking ALL the spotlight away from her new album ... and she bitched about it last night ... on tape.

Fiona was performing at the House of Blues in New Orleans -- and before she kicked off her set, she addressed the crowd, saying, "This record with me ... I'm really sorry ... All the work we did is being overshadowed by this bulls**t."

Fiona's obviously referring to her Texas drug bust last week, when she was allegedly popped with a baseball-sized chunk of weed and a bunch of hash. According to cops, Fiona admitted the drugs were hers.

Fiona then ignited a firestorm by publicly blasting 4 police officers for allegedly mistreating her during the arrest. In a bizarre moment on stage the other night ... She said she kept a log of the abuses in a "lockbox" and planned to use it against the officers.

But last night she took it all back, saying ... "There are no f**king lock boxes. I didn't make up a code. It was my way to make a parallel between the south. I am not that f**ked up."