Clerical Supreme Leader Ayatollah Ali Khamenei has tightened his grip on Iran's faction-ridden politics after loyalists won over 75 percent of seats in parliamentary elections at the expense of President Mahmoud Ahmadinejad, a near-complete count showed.

The widespread defeat of Ahmadinejad supporters - including his sister, Parvin Ahmadinejad - is expected to reduce the president to a lame duck after he sowed divisions by challenging the utmost authority of Khamenei in the governing hierarchy.

The outcome of Friday's vote, essentially a contest between conservative hardline factions with reformist leaders under house arrest, will have no big impact on Iranian foreign policy, notably its nuclear stand-off with the West. But it will boost Khamenei's influence in next year's presidential election.