There are more than 3,400 candidates competing for 290 seats in the Iranian Parliament in an election scheduled for Friday. Human Rights Watch alleges that nearly 2,000 candidates were rejected because of "ill-defined criteria."
The rights group said opposition figures are either barred from competing or promised to boycott the election.
"Iranian authorities have stacked the deck by disqualifying candidates and arbitrarily jailing key members of the reform movement," Joe Stork, deputy Middle East director at Human Rights Watch, said in a statement from New York. "There is no transparency surrounding the vetting and selection of candidates."
The rights group said an Iranian election committee disqualified some parliamentary candidates because of their "lack of adherence to Islam and the Constitution."
Iranian Supreme Leader Ali Khamenei, British newspaper The Daily Telegraph said, called on supporters to vote against Ahmadinejad supporters.
Radio Zamaneh, a Dutch broadcaster sympathetic to the Iranian opposition movement, reports that Ali Akbar Javanfekr, a media adviser to Iranian President Mahmoud Ahmadinejad, was sentenced this week to one year in prison for "insulting" Khamanei.