The conservative Islamic Engineers Society in a letter to Iranian President Mahmoud Ahmadinejad said he had "acted against his own interest" by appointing a former vice presidential nominee to head his personal office.
Ahmadinejad announced he would reshuffle his Cabinet in the wake of the June 12 presidential election, nominating Esfandiar Rahim-Mashaei to replace Parviz Davoudi as the first vice president.
Rahim-Mashaei sparked controversy over comments he made in 2008 suggesting Iran was a friend of the Israeli people.
Ahmadinejad reversed his decision following the intervention of Supreme Leader Ali Khamenei but ultimately appointed Rahim-Mashaei, a close confidant, to head the presidential office.
The conservative group in its letter to the president said it was troubling that Ahmadinejad had made his decision "without any insight," which had "caused divisions" among the ruling elite, state-funded broadcaster Press TV reports.
The letter went on to remind Ahmadinejad that it was political confrontation that ultimately led to the ouster of former Iranian Prime Minister Mohammad Mossaddeq, toppled in a 1953 coup, and former President Abolhassan Banisadr, who was impeached in 1981 for his clerical opposition.
"It seems you want to be the sole speaker and do not want to hear other voices," the letter said. "Therefore it is our duty to convey to you the voice of the people."