The 12-member Guardian Council is vetting candidates from a list of about 600 hopefuls who submitted their interest in replacing Mahmoud Ahmadinejad, who's ineligible to compete because of term limits, as Iran's president.
Rafsanjani, a 78-year-old former president with a long history in Iranian politics, entered the race at the last minute, backtracking on a suggestion made last year that he wouldn't run for high office again.
Parliament member and conservative candidate Alirez Zakani said Rafsanjani wasn't the best candidate in the field.
"Despite his services in the past, Mr. Hashemi has proved that he is a man (prone to) huge mistakes," he was quoted by Iran's state-funded broadcaster Press TV as saying.
Rafsanjani was criticized for siding with former Iranian Prime Minister Mir Hossein Mousavi during the 2009 campaign. Mousavi was the focal point of the so-called Green Movement, which rallied in opposition to Ahmadinejad.
Zakani said that conservatives should band together despite his sentiment that Rafsanjani wasn't the right person for the job.
Iranian elections are scheduled for June 14.