Statistics published by the Department for Education show that a total of 4,690 looked-after children were adopted in 2016, compared with 5,360 in 2015, a fall of 12 per cent.
It is the first annual fall in numbers of adoptions since before 2012, but was largely expected due to a significant drop in the number of children being placed for adoption in recent years.
The fall in adoption placements is widely accepted to stem from a ruling made in September 2013 by Sir James Munby in the case Re B-S in which he criticised the "sloppy practice" of social workers and said that local authorities must provide evidence that all alternatives to adoption had been considered before bringing a case to court.
Hugh Thornbery, chief executive of Adoption UK, said: "I've feared for some time that there would be a dramatic fall in adoptions this year so the drop comes as no surprise. We expect to see a further fall in the current year.
"Adoption can offer the best chance to permanently break a cycle of neglect and abuse and give a child a second chance at fulfilling their potential with the support of a loving family - so we cannot stress enough the importance of clearing up any confusion over the 2013 rulings which has undoubtedly had a negative impact upon adoption decisions and placement orders in recent years."
The statistics also show that the number of looked-after children is continuing to rise, having increased steadily over the last eight years.
There were 70,440 looked-after children as of 31 March 2016, an increase of 1 per cent compared with 31 March 2015 when there were 69,480.