A federal government ban on retained phone and internet records being used as evidence in family violence civil proceedings has been warned to have potentially "catastrophic" consequences.
Legislation requires telecommunications companies to keep data for at least two years.
Law enforcement and security agencies are able to access the data under strict controls and use it in criminal proceedings, but the government has ruled out allowing admission in civil cases following a review which considered more than 260 submissions.
Federal Attorney-General George Brandis said the review had found there was insufficient reason to justify making exceptions.
The ACT Justice and Community Safety Directorate submission asked for exceptions to be made in "serious civil proceedings".
The directorate said communications records had been subpoenaed previously in domestic violence matters, coronial inquests and workers' compensation cases involving bullying.
The ACT submission argued the impact of prohibition in some civil proceedings could be catastrophic.
"The rationale ... is that these types of proceedings can lead to criminal sanctions and the behaviour of concern is often akin to, or overlaps with, criminal conduct [eg stalking, harassment]," the directorate said.
"Family and children's safety is supported through the protection order process, which relies on the ability of the system to make fully informed assessments of risks."
The directorate said there were sometimes related civil and criminal proceedings where inconsistent evidentiary rules could cause confusion, delay and higher cost.
The Commonwealth's response points out the ACT did not provide details on how telecommunications data had been used in past proceedings.
"Given the limited practical evidence about the degree to which telecommunications data has been useful in these types of matters, it is difficult to determine the strength of the case for access in these circumstances at this time," the response says.
"Further consultation and evidence would be needed to properly assess the case for exceptions to the prohibition in such circumstances."
The government also rejected an Australian Federal Police suggestion to exempt law enforcement-related civil proceedings from the ban.
The AFP cited examples including proceeds-of-crime matters, child protection orders and apprehended violence orders.
The government said exceptions could be considered later if new evidence emerges.
The story Metadata evidence ban could be 'catastrophic' for family violence cases first appeared on The Sydney Morning Herald.