Just 57 people were jailed for human trafficking last year, the lowest total in 10 years, despite police and justice ministry efforts to crack down on the practice, the AD said on Monday.
In 2005 more than 200 people were sent to jail for trafficking and human smuggling, but by 2014 this had gone down to 60.
Courts are also imposing shorter sentences. Last year four people were sent to jail for longer than a year, compared with seven in 2014, the AD said. In total 90 cases involving human trafficking were taken to court in the Netherlands last year. This too is a drop on previous years.
Junior justice minister Klaas Dijkhoff on Friday described human trafficking as a government priority and said the extra border checks introduced since large numbers of refugees began arriving from the Middle East were having an impact.
Some 30 people have been arrested as a result of those checks and these cases still have to be processed, so are not included in the 2015 figures.