Sussex Police processed 10,633 enhanced DBS applications in September, an increase from 6,436 in the same period the previous year.
A spokesman for the force said it had experienced delays due to an increased demand and a period of high staff turnover.
“We recognise the impact these delays have,” he said.
“Our priority will continue to be the quality of safeguarding work to ensure the safety of the community and fairness to all applicants.”
A DBS spokesperson said the average time to process enhanced applications in September was 11.7 days.
“A small number of forces are currently experiencing delays in completing checks. Measures have been introduced to support capacity at a small number of forces who are experiencing backlogs,” they added.