Foreign workers who come to Sweden without a work permit have little or no opportunity to protest against the bad working conditions and can't turn to authorities for help or advice.
Swedwatch argues that in order to diminish the risk of foreign pickers being taken advantage of, coming to Sweden to work without papers should no longer be considered a criminal offence.
The organization also calls for wholesalers to take more responsibility for the working conditions of their foreign labour.
The group also wants to see ways to ensure that potential foreign berry pickers receive more and better information before coming to Sweden.
Sweden has recently cracked down on the practice, implementing stricter rules for recruiment agencies that bring in foreign labourers into the country.
The efforts have led to some improvements in the situation for berry pickers working in Sweden legally.
While Swedwatch isn't sure how many undocumented labourers have been working in Sweden this season, the organization estimates the number to be close to 2,500, the organization's Viveka Risberg told news agency TT.
The figure is based on the fact that the number of pickers that came to Sweden through legal channels was halved from about 5,000 to 2,500 compared to last year, while the amount of berries purchased didn't diminish during the same period.
Most of the undocumented labourers came from Asia, with the majority from Thailand, and many had applied for tourist visas in Sweden to visit relatives.
According to Swedwatch, there is a huge market for false papers and letters from made-up relatives which are used when applying for visas.
Pickers have also allegedly paid out huge sums to intermediarys in order to be able to travel to Sweden.