The call came in a resolution adopted on 26 January by PACE after parliamentarians discussed the human rights situation in Belarus.
The PACE also expressed its support for the country's democratic opposition ahead of presidential elections due on 19 March.
The elections are not expected to unseat President Alyaksandr Lukashenka.
Addressing the assembly, opposition leader Alyaksandr Milinkevich said that "today, there is no democracy in Belarus" and that Belarusian society is "paralyzed by fear."
"Can the election be free in a situation where criticism of the authorities is considered to be an attack against the state? And, since January this year, it is considered a criminal act. Can [the election] be free in a country where independent radio and television do not exist?" Milinkevich asked.
The Parliamentary Assembly stressed the need to more actively support the "consolidation of the democratic opposition" and called on other international organizations -- including the EU and the Organization for Security and Cooperation in Europe (OSCE) -- to come up with joint strategies to assist democratization processes in Belarus.
Speaking in Strasbourg, where the PACE is seated, the speaker of the Belarusian parliament Uladimir Kanaplyou said there will be no color revolution in Belarus, a reference to Georgia's Rose Revolution, Ukraine's Orange Revolution, and Kyrgyzstan's revolution, most commonly referred to as the Tulip Revolution but sometimes as the Lemon, Yellow, or Pink Revolution.
(Interfax, ITAR-TASS, AP)