Ali Zabihi was quoted by the Italian news agency ANSA as saying there had been two plans to first abduct and then murder Ahmadinejad.
He said the plots concerned Ahmadinejad's visits to Baghdad in March and to Rome earlier this month for an international food conference. "Both these plots were prevented by the will of God," Zabihi said.
He also said U.S. President George Bush had ordered the alleged assassination attempts.
"The policies conducted by Ahmadinejad throughout his rule have clashed with the illegal interests of certain foreign powers and a number of inner Iranian circles. That is why plots to kill him were organized," he said.
Ahmadinejad himself said last week that an assassination attempt had been planned during his visit to Baghdad. "According to reliable intelligence data, our enemies planned to kidnap and kill the servant of the Iranian people during his visit to Iraq," he said, referring to himself.
The Iranian president added that changes to his schedule during his Baghdad visit had prevented the assassination attempt.
Western nations have accused Iran of pursuing a secret nuclear weapons program. Iran has denied the allegations, saying it needs nuclear energy for civilian purposes.
