"Freedom is the essence of human being I believe, in fact without freedom no choice has a meaning," he says in the 15-minute-plus video.
The video was recorded recently on a mobile phone and posted on YouTube. It was then quickly shared on Facebook, blogs, and other social media sites.
Tabarzadi the head of the banned Democratic Front of Iran who has been in and out of prison for the past several years, is currently serving an eight-year prison sentence after being convicted of security charges that are often being brought against Iranian political activists.
In the video, Tabarzadi says the Iranian leadership fears individuals like him who have resorted to nonviolent means to bring change in the country.
He says the harsh methods Iran uses against political activists, students, and human rights advocates are doomed to failure:
"We are not terrorists; we are not promoting violence; we have said certain things based on our basic rights; we've expressed our views. The establishment issues heavy prison sentences against us out of fear, it fears what we have to say -- the things we're saying here between us. I don't believe the crackdown, violent measures, prison and other things will stop us. We're determined, we have paid a price, and we're [ready] to pay an even higher price, we know our rights, and we will definitely reach our demands. "
Tabarzadi adds that Iranians deserve a democratically elected secular government that will respect the rights of all citizens.
Tabarzadi's video message is an example of social media providing Iranian activists a platform on which they can express themselves more freely than through other, frequently heavily censored media.
It comes just a few days after another video was posted on YouTube that shows a number of prominent Iranian political prisoners in the courtyard of Gohardasht prison.
It is still unclear what repercussions the outspoken Tabarzadi might face over his video message, which is likely to draw the ire of Iranian authorities.
Activists have been increasingly using social media, particularly Facebook, to spread news and bring attention to the plight of Iranian political prisoners since the crackdown began after the 2009 presidential vote.
An increasing number of prisoners of conscience have in recent months issued open letters from prison in which they have described mistreatment and torture by the hands of their interrogators. The letters have been distributed widely through social media.
A number of them have dared to challenge Supreme Leader Ayatollah Ali Khamenei, who holds ultimate political and religious power in the country.
We reported recently about the efforts of former political prisoner Mohammad Nourizad, who used to be a columnist for the ultra-hard-line "Kayhan" daily, which is said to reflect Khamenei's views.
Nourizad has challenged Khamenei in 15 open letters, including several from Evin prison. He has called on others to do the same.
Another prisoner of conscience, Abolfazl Ghadiani, who was arrested in 2009, last week in an open letter issued from prison called on the Iranian leader to step down and give up power.
"People like myself have not given our life, livelihood, and freedom in the path of the revolution for Ali Khamenei to reign over the country," Ghadiani, a member of the reformist Mujahedin of the Islamic Revolution party, wrote in the letter. He blamed Khamenei for Iran's dire economic situation, sanctions, and the specter of war that has spread its shadow on Iran.
-- Golnaz Esfandiari