The Coordination Council of Green Path of Hope issued the call on the anniversary of a protest last year that attracted tens of thousands of people and led to the house arrest of opposition leaders Mir Hossein Musavi and Mehdi Karrubi.
The council has called for demonstrations in the intervening 12 months, but those calls have triggered tight security measures by the Iranian establishment and failed to draw opposition activists out into the streets.
Musavi adviser and Coordination Council of Green Path of Hope spokesman Ardeshir Amir Arjomand told Radio Farda that the Iranian establishment, which has heaped praise on the so-called Arab Spring demonstrations in Egypt and Tunisia, should grant Iranians the right to protest.
We're in a very difficult and dangerous situation, we have to do all we can to change the situation," Arjomand said. "The economy is mismanaged, there’s growing poverty, [and] economic structures are collapsing."
He described Iran’s international status as "shrinking significantly" and said his country is "facing major threats."
"Because of all these issues, we need to change the situation and bring people to the scene so that their voices of protest can be heard by the establishment," Arjomand said.
The Green Movement is an initiative led by Musavi that emerged after the disputed reelection of President Mahmud Ahmadinejad in June 2009 and massive street protests challenging the result.
But the ensuing crackdown -- which included disappearances and allegations of torture, police sweeps, and televised mass trials -- has led opposition supporters to engage mostly in online protests rather than street demonstrations. More recently, security forces have outnumbered the few protesters who have dared to come out.
The Green Movement -- hobbled by the house arrest of founder Musavi -- has not been present as an organized force but its sympathizers have maintained their demands.
Based on reporting by RFE/RL's Radio Farda and RFE/RL