Iraj Abdi told IRNA that in their letter, the lawmakers have called on the judiciary chief to strongly respond to such self-motivated moves.
Motahhari, a moderate member of parliament, was due to deliver a speech at Shiraz University in central Iran when his car was attacked by unknown motorcyclists.
He is member of parliament from Tehran and a vocal critic of the former president Mahmoud Ahmadinejad for bringing the enemies of the country together to inflict a major blow to the nation by orchestrating sanctions.