"Stifling the media, filling the prisons and brutally killing people who peacefully demand their rights in the streets indicate the roots of tyranny and dictatorship remain from the monarchist era ... I don't believe that the revolution achieved its goals."
Mousavi's comments follow the execution by hanging of two people in connection with the unrest that erupted in the wake of the disputed presidential vote in June last year.
Allegations that the vote - it saw Mahmoud Ahmadinejad, the incumbent president, re-elected - was rigged sparked widespread street protests and pitched Iran into one of the worst crises in the Islamic republic's history.
The two men executed on Thursday in connection with the violence were identified as Arash Rahmanipour and Mohammad Reza Ali-Zamani.
Both were reported by Iranian media as belonging to the monarchist group Tondar, also known as the Kingdom Assembly of Iran.
The executions drew international condemnation and were branded by opposition leaders as an effort to scare protesters and keep them off the streets.
Alireza Ronaghi, Al Jazeera's correspondent in Tehran, said that Mousavi, who has spearheaded the anti-government protests since the elections, likely made the comments to bolster his supporters' morale following the executions.
"He's saying that part of the objectives of the revolution that are crystallised in Iran's constitution - including human rights and people's rights to free expression and freedom for peaceful gatherings - are being neglected," he said.
"That will definitely been received with a lot of noise within the conservative camp.
"They will try to analyse what Mir Hossein Mousavi said as another sign of him being behind all the unrest and that he - and the other opposition leader Mehdi Karroubi - [are] acting as a proxy for global arrogance and Western powers, including the United States and Britain."
Tehran has said it will "soon execute" another nine people arrested during anti-government protests.
Mousavi made the remarks in the run-up to the 31st anniversary of the 1979 Islamic revolution on February 11.
Celebrations marking the revolution and the 1979 return from exile of Ayatollah Ruhollah Khomeini began on Monday.
They will climax on February 11 with a state-sponsored march to mark the anniversary of the fall of shah who had ruled Iran for nearly four decades.
More opposition demonstrations are planned to coincide with the event.