"Dr Mahmoud Ahmadinejad is nominated by the Osulgharayan bloc in parliament to be the fittest candidate for the presidency," the report said in reference to Friday's presidential poll.
The Osulgharayan (Principalists) group, the majority bloc in the 290-seat parliament, had late May failed to reach consensus on which presidential candidate to back.
The group in a statement carried by IRNA praised Ahmadinejad for "standing firm against bullying … and Westernisation and for not giving in to the West as urged by the supreme leader (Ayatollah Ali Khamenei)."
Khamenei in May implicitly came out in support of Ahmadinejad by urging voters not to elect a candidate who could adopt a pro-West stance.
It would be a "catastrophe" for Iran, Khamenei said, if a candidate who "thinks about endearing himself to some Western power or an international arrogant" is elected president.
Ahmadinejad's presidency has seen Iran adopt an aggressive stance towards Western powers, especially the United States.
The hardliner had earlier won the support of other conservative groupings in the Islamic republic, including the Followers of Imam and Leader's Line — a coalition of 14 conservative parties.
The Qom Seminary School Scholars Association, one of the leading conservative clerical establishments, in May announced it would back Ahmadinejad although support was not unanimous.
Another powerful clerical establishment, the Militant Clergy Association, last month announced its support for the incumbent president.
Ahmadinejad faces a challenge from former premier Mir Hossein Mousavi, ex-parliament speaker Mehdi Karroubi and former Revolutionary Guards chief Mohsen Rezai in Friday's poll.
