Nelly Accuser Blasts UK Police Force for Botching Investigation

The woman accusing Nelly of sexual assault in the UK thinks cops who've been investigating have royally screwed things up to the point she doesn't care if they finish the probe or not.

In a letter obtained by TMZ, the attorney for the anonymous accuser -- who goes by Jane Doe -- put the lead detective of the Essex Police on blast, claiming he'd completely botched the investigation by treating her client like a suspect instead of a victim.

The lawyer outlines what she says were the sequence of events in the case over the past year as the Essex Police looked into Jane Doe's claims -- namely, that Nelly allegedly masturbated in front of her and forced his penis in her mouth after one his concerts in 2017. Nelly says her story is BS.

In her letter, Jane Doe's lawyer claims the police have asked for the alleged victim's phone records, including all of her pictures, texts and emails between herself and the attorney ... who points out that violates attorney-client privilege under U.S. law.

Not only that ... the attorney says the police have asked Jane Doe to do a follow-up interview to the one she's already done, showing up to her house unsolicited and trying to coax her into coming to the police station again. Meanwhile, the attorney notes that they took an entire year to get Nelly to come out to interview with them, dragging their feet the whole time.

Jane Doe's attorney says the Essex Police are probably intimidated by Nelly and his high-powered lawyers, and accuses them of being completely incompetent in coming to a resolution.

She says that because Jane Doe has already filed suit against Nelly over the alleged assault, they will no longer be participating in the Essex Police's probe.

Originally Published -- 6:40 AM PT

9:06 AM PT -- The Essex Police tell TMZ, "We can confirm we have received communication from a solicitor regarding the case and will be reviewing this investigation and engaging with both parties in due course."