In a televised debate with his main challenger Mir Hossein Mousavi a week ago, Ahmadinejad charged that some Mousavi supporters, including sons of Rafsanjani, had received financial privileges in the past.
A furious Rafsanjani fired off a letter of protest to supreme leader Ayatollah Ali Khamenei and said he had also personally told Ahmadinejad to take back the remarks.
"I also asked state television to allocate time to defend those accused according to the law… but these suggestions were not accepted and the (supreme) leader chose to remain silent," Rafsanjani wrote.
"However the young need to know the truth," he said in the letter, which was published in local newspapers.
Iran has been airing a series of almost unprecedented televised debates between candidates ahead of Friday's presidential election, in which Ahmadinejad is bidding for a second four-year term.
Rafsanjani, a former president who was appointed by Khamenei to head the powerful Expediency Council — Iran's top political arbitration body — has threatend to sue Ahmadinejad.
"Unfortunately, Mr Ahmadinejad's irresponsible and untruthful remarks in the debate are a reminder of the bitter remarks of monafeghin (hypocrites) and anti-revolutionaries during the early years of the Islamic revolution," the cleric wrote.
Rafsanjani, who was defeated by Ahmadinejad in the 2005 election, urged Khamenei to step in and resolve the spat.
"I ask your eminence, given your position, responsibility and personality, to solve this problem and act in a way you deem right to take effective action in eliminating the mutiny," he said.
