An escalation in the number of calls from Ms Chambers in the two months before the murders in June last year was also missed by the force, the report found.
The IPCC said while individual officers could have done things better, it was a failure of police systems rather than of individuals.
IPCC Commissioner Rachel Cerfontyne said: "The deaths of Christine and Shania Chambers are shocking to us all. It is impossible to say with any certainty whether if individual officers or the force had done things differently, Ms Chambers and Shania would still be alive today.
"While individual police officers could and should have done things better, this is not essentially a failure of individuals, but a failure of systems. The investigation identified a lack of adequate training, insufficient resources allocated to domestic violence cases and poor oversight.
"This is a tragic and disturbing case and the investigation has identified several key issues which apply to many other cases where domestic homicide is the outcome.
"Many women are reluctant to pursue criminal proceedings against abusive partners, sometimes even to seek help at all. There are many reasons for this, and often it is fear that they will exacerbate the situation and increase the danger they face.
"Undoubtedly this poses significant challenges for the police and other agencies, but it is essential in these situations that all possible is done to protect the victims and their children.
"Unwillingness to seek help or give evidence against the perpetrator is often due to fear and can be a sign of vulnerability, not culpability, and this must be recognised when a risk assessment is completed."
Responding to the report, which was released today, Essex Police said it accepted the findings and apologised for the failings which had been identified.
Assistant Chief Constable Maurice Mason said: "On behalf of everyone at Essex Police, I extend our deepest sympathies to the family and friends of Christine and Shania Chambers, who were brutally murdered by David Oakes in the early hours of June 6 2011.
"Essex Police accepts the findings of the IPCC report, and apologises for the failures identified there.
"Every police officer involved in the case of Christine and Shania is devastated by their passing. I too am devastated by their deaths. I became a police officer to protect the vulnerable, and to put criminals like Oakes behind bars.
"Essex Police is committed to working tirelessly to reduce the likelihood of tragedies such as this from occurring again."
He added: "The unbelievable inhumanity of these murders led Oakes to be sentenced to two whole-life prison terms - the most extreme punishment which the British judicial system can impose.
"You would think that a man capable of such horror would have a history of violence. Oakes did not: he had no convictions or cautions for violence.
"In fact, the Independent Police Complaints Commission has found that significant 'information concerning Oakes's violence towards Christine Chambers was not available to the police or social services'.
"The IPCC also stated that there was no information that Oakes had access to a firearm. Essex Police acts promptly and decisively whenever it receives credible intelligence about illegally-held weapons.
"Essex Police accepts the report of the IPCC and welcomes the recommendation that processes should be developed for better information sharing between police forces and agencies such as social services, courts and solicitors. This is particularly important in cases involving child custody proceedings, where allegations of domestic violence have not been reported to officers.
"It should be stressed that the IPCC investigation found that it is impossible to say with any certainty that, if the force had done things differently, Christine and Shania would be alive today. It also found no evidence of misconduct by any of our officers."
Following the release of today's report, Ms Chambers' father Ken praised Essex Police for its support during the murder investigation but said he felt the force could have done more to prevent the deaths.
Mr Chambers said: "As a family we would again like to say thank you to all those, including friends and neighbours, who have shown us such support and kindness since the murders of Christine and Shania.
"We have also received marvellous support from the police murder investigation team led by Detective Chief Inspector O'Toole, from police family liaison officers and the victim support service, and we are grateful to all of them for helping us through such a traumatic time.
"We have been kept informed by the IPCC of their investigation and findings and have had opportunity to read through and discuss their report.
"We realise one evil man is responsible for taking Christine and Shania away from us and not having them in our lives any more remains extremely difficult to bear.
"While we understand at times Christine could have been more cooperative with the police, we do feel that Essex Police could have done more to prevent the deaths; they should have taken greater steps to protect Christine; for instance we are still of the view she should have had a panic alarm installed at her home which may have allowed her to summon assistance at a crucial time after her phones had been smashed. And we think that officers dealing with ongoing incidents should have been more aware of the history and should have better identified the risks."
