The duration for the quarter April to June 2019 is the highest since the final quarter of 2013, and since the 2014 introduction of the 26-week target for care and supervision proceedings in the family courts.
The limit, which can be increased in certain circumstances, was put in place under the Public Law Outline after case durations peaked at 55 weeks in 2011.
While the impact of the guidance was significant, times have gradually crept up and the recent numbers show a three-week rise on the same quarter last year.
The percentage of cases completed within the target time has dropped from 48 per cent to 41 per cent, compared with the same quarter in 2018.
However, the rise in case duration comes alongside a year-on-year drop in the number of cases in the system.
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The quarterly figures show a five per cent drop in public law applications on the same period in 2018, with applications made in relation to 8,562 children.
There was a seven per cent fall in the number of public law orders, with 10,745 children involved in orders.
The figures indicate a recent trend of falling care applications following a period of rapid growth.
The statistics also reveal the number of adoption applications and orders dealt with by the family courts has fallen, reversing a six-month period during which numbers were rising.
During April to June, there were 1,230 adoption applications made, down two per cent from the same period in 2018.
Over the same period, the number of adoption orders issued dropped by six per cent to 1,202.
Male and female couples remained the largest type of adopter (60 per cent) while 20 per cent of adoption orders were granted to sole applicants, 14 per cent to same-sex couples and a further six per cent to step-parents.
In contrast, the number of domestic violence remedy applications and orders showed an increase of 16 per cent for the period April to June compared with the same quarter last year.
There were 7,113 applications, of which most were for non-molestation orders (82 per cent) compared with occupation orders (18 per cent).
Increases were also recorded for forced marriage protection orders and female genital mutilation protection orders, indicating a general upward trend.
Although numbers remain small and fluctuating, there has been an increase since they were introduced in 2008, the report says.
For the period April to June, there were 95 applications, of which 77 per cent of applicants were aged 17 and under. Over the same period, there were 167 orders made, more than double the same period the previous year.
The Children and Family Court Advisory and Support Service (Cafcass) said it supported extensions to the 26-week limit where necessary, but cautioned against "drift".
"The need to manage demand has been a key theme of the judicially-led working groups, established to look at practices and processes in family court proceedings," added the service.
"Cafcass supports an extension of the 26-week limit in cases where that is in the best welfare interests of the child, for example when further time could provide a permanent home for a child to live but where additional assessment is required or where parental capacity to change requires multidisciplinary support and further time.
"But this extension must have clear purpose and not lead to unnecessary drift."