Out of 272 present lawmakers in the parliament on Sunday, 192 voted against the labor minister, Abdolreza Sheikholeslami. The chamber has 290 seats.
The lawmakers are angry over the labor minister's decision to appoint Saeed Mortazavi as head of Iran's social security fund. A parliamentary probe in 2010 found that Mortazavi, then chief Tehran prosecutor, was responsible for the deaths of at least three anti-government protesters who were tortured.
In response, Ahmadinejad turned the tables on his conservative opponents and accused parliament speaker Ali Larijani and his relatives of misusing power. Ahmadinejad played a barely audible videotape showing Larijani's brother, Fazel, in a meeting where he allegedly sought a bribe in return for ensuring the support of the speaker and another brother, Sadegh Amoli, who is chief of judiciary.
Larijani denied the charge saying he has no business relation with his brother. He accused Ahmadinejad of having a "Mafia-type" attitude and disregarding the country's dignity, law and ethics. "It was a good thing that you showed this to let people to learn about you character," he said.
The dispute was seen a way to damage Ahmadinejad ahead of presidential election in June. Under the law, Ahmadinejad cannot run for another term, but his opponents say he is trying to impose a hand-picked successor on them.
For the first time in the country's history, the parliament grilled the president in March 2012 over the alleged mismanagement of the nation's economy. They also questioned Ahmadinejad about his decision to dismiss an intelligence minister in May 2011—a move seen as a defiance of the country's top leader Ayatollah Ali Khamenei. The minister was reinstated later at Khamenei's instruction.
Since then, many of Ahmadinejad's former supporters have started backing his conservative opponents.