According to the organisation's report on social care staffing, 16 percent of social workers in council adults' services roles quit or changed job, representing a rise on the year before's 13 percent.
However, the number of social workers employed in adults' services departments - 16,100 - remained the same as it was in 2015 and vacancy rates dropped from 12 percent to 11 percent.
The average social worker salary also rose from £32,800 to £33,100, representing a one percent rise in cash terms.
A major trend identified in NHS Digital's report was the moving of wider social care roles from councils to the independent sector, with the number of local authority adults services jobs dropping six percent from 120,200 to 112,800.
And though 86 percent of social worker jobs remain in local authorities, restructures and service closures mean that over three quarters - 78 percent - of adults social care posts are in the independent sector.
The President of the Association of Directors of Adult Social Services, Margaret Wilcox, cited social care budget cuts of £5.5bn as a major factor behind the figures.
She said: "Despite these huge pressures, councils have sought to protect front-line social workers while seeking efficiencies in management and outsourcing direct care provision.
"Care staff and social workers are pulling out all the stops to provide personal and dignified care to those who need it, with the report showing that nearly half (44 percent) of adult social care workers had no days off sick in a year.
"This significant fall in staff numbers is unsurprising and is due to the social care funding crisis which is failing to tackle the growing demand within local communities for care of people living longer and with increasingly complex needs."