A draft report by the Independent Police Complaints Commission (IPCC), seen by the BBC, found police and prison authorities failed to respond to reports that Moat had threatened to hurt Samantha Stobbart during his time in Durham Prison.
After his release, the 37-year-old shot and injured Miss Stobbart, killed her new partner, and blinded the police officer David Rathband. He had been serving a sentence for assault.
The unpublished IPCC report allegedly found Moat had made specific threats to shoot a number of people including Miss Stobbart and Chris Brown when talking to another inmate.
The prisoner had told an officer of the conversation but had not been able to recall the exact words. A report by a prison officer in a Security Information Report later said Moat had intended to "seriously assault" his former partner.
But the report on the threats was passed to prison in-trays. Police did not act on one warning from the prison, while it did not read another, the IPCC found.
The report said: "What remained unanswered was a threat by Raoul Moat that he was going to do serious harm to his partner whoever that proved to be."
The IPCC said there was no evidence of misconduct but said the shortcomings were a performance issue.
Ch Supt Neil Adamson, of Northumbria Police, told the BBC: "Officers were faced with a very limited piece of information from Durham Prison.
"I want to make it clear from the outset at no stage did that ever suggest there was a real and immediate threat to life."
He added: "To try and suggest that we could have prevented that I think is a step too far. I am convinced he would have done what he intended doing, such was his focus."