IRNA said conservatives MPs parliament chose Larijani by 161 votes against 50 for the incumbent Gholam Ali Hadad Adel, who is also a conservative.

Conservatives have the majority in the new parliament after winning 69 percent of the 290 seats in elections earlier this year.

Their reformist rivals, who have not yet named any candidates for the post of speaker, only secured 16 percent of the seats while another 14 percent went to independents.

Parliament has to vote on the new speaker after its first session on Tuesday.

Larijani last year stepped down as Iran's top nuclear negotiator, admitting that policy differences between himself and President Mahmoud Ahmadinejad were so great they could no longer work together.