Serious failings in the management of domestic abusers living in the community are laid bare in a major new report.
Inspectors found contact with offenders was too infrequent, leaving many to "drift" through their supervision without being challenged over their "predilection" for violence.
Staff often underestimated the level of harm victims were exposed to and there were "grave concerns" about some practices, the assessment warned.
In seven cases, a watchdog demanded immediate action to ensure the safety of victims and children.
HM Inspectorate of Probation found poor practice was widespread in community rehabilitation companies (CRCs), which supervise thousands of low and medium-risk offenders across England and Wales.
Chief Inspector Dame Glenys Stacey said: "Too often we were left wondering how safe victims and children were, especially when practitioners failed to act on new information indicating that they could be in danger.
"It is not an exaggeration to say that many individuals were drifting through their supervision period without being challenged or supported to change their predilection for domestic violence.
"CRCs play a crucial role in supervising perpetrators of domestic abuse and we found they were nowhere near effective enough."
The report assessed arrangements for supervising perpetrators of domestic abuse after they are released from prison or sentenced to a community order.
Inspectors examined 112 cases and found:
- In seven out of 10 (71%), work to protect victims and children was not good enough
- Home visits were often considered a "luxury" - in instances where they should have taken place, fewer than one in five (19%) had been completed
- Only 27% of eligible offenders had been referred to an accredited programme designed to prevent further abuse - leading some staff to create their own alternative courses.
Work to protect victims and children was poor, the Inspectorate concluded.
It cited examples including a case where a man was sentenced to a community order for assaulting his partner.
After evidence emerged that he was back at the family home, no action was taken to liaise with police or visit the property - leaving the victim and her children "unprotected", the report said.
In other findings, it detailed how some meetings took place in public spaces such as cafes, which "limited the scope to explore and address sensitive and personal issues", and warned many staff had "unmanageable workloads".
Overall, the watchdog said it was a concerning picture, with only "pockets" of good practice.
Women's Aid Chief Executive Katie Ghose said the report shows CRCs are "failing victims" and are "currently not fit for purpose when it comes to domestic abuse cases".
She added: "We call on the government to urgently change this to protect survivors."
Ministers overhauled the arrangements for supervising offenders in 2014.
The partial privatisation saw the creation of the National Probation Service to deal with high-risk cases, while remaining work was assigned to 21 CRCs.
But the programme has been dogged by criticism.
In a report last year, the inspectorate revealed thousands of offenders living in the community were being managed by a brief phone call every few weeks.
In July, the Ministry of Justice announced plans to end the contracts in 2020 - two years early.
Under a proposed new system, 10 probation regions would be created in England, with each containing one NPS division and one CRC. In Wales, the NPS would assume responsibility for the management of all offenders.
Prisons and Probation Minister Rory Stewart said: "We are taking decisive action to improve CRCs by ending current contracts early, investing £22 million in through the gate services, and we have consulted on how best to deliver probation services in the future.
"This report highlights pockets of good practice to build on, but more must be done.
"By putting in place new arrangements, we will heed the lessons from what has and hasn't worked, so probation plays its full part in tackling domestic abuse and protecting victims."
Mr Stewart also highlighted the Government's proposed Domestic Abuse Bill, saying it will improve victim support and bring more offenders to justice.
Findings from the 2016/17 Crime Survey for England and Wales show nearly two million adults experienced some form of domestic abuse in the previous year.
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