Every month the bank asks firms across the economy about things like staffing levels, order books and exports.
In August overall business activity fell for the second month in a row.
The bankʼs chief economist Richard Ramsey said the survey pointed to a generalised slowdown across the UK.
"Only two UK regions recorded growth in output last month. Northern Ireland is at the bottom of the list, with the sharpest rates of decline seen across the UK," he added.
The survey suggests that activity fell in each of the four broad sectors of the Northern Ireland economy - services, manufacturing, retail and construction.
The main positives to be drawn from the survey are that businesses are continuing to recruit and remain confident that economic conditions will improve over the next 12 months.
Later this week the Northern Ireland Statistics and Research Agency will publish official data on the performance of the Northern Ireland services and manufacturing sectors in the second quarter of the year.
There will also be the latest monthly employment data.