The Tunisian Organisation Against Torture (OCTT) reported 153 torture cases in the North African country from January to November.
There were 250 cases in the previous year.
In a report, it accused authorities of abuses including arbitrary arrest, ill-treatment and threats or attempts at rape.
OCTT president Radhia Nasraoui called for new laws to prevent torture.
“Political parties, whether in power or in opposition, must expose the subjects of violations and human rights,” she said.
Last year, a group of UN experts said torture was still an issue in Tunisia but the country was “on the right path” to tackling it.