Gholam Hossein Elham has been under fire since he rejected reports the economy and interior ministers were to be sacked as an "April fool's joke" before confirming days later they were being asked to step down.
"I voice my readiness to withdraw from all government positions," said Elham, a key aide of the president, in a letter to Ahmadinejad released by the presidency and quoted by the Fars news agency.
It was not clear if Ahmadinejad would accept his resignation.
The letter comes two days after a state television news report ridiculed Elham's handling of the reshuffle plans and his holding of several jobs which also include the post of justice minister and a seat on the Guardians Council.
"Maybe by holding several different posts, Mr Spokesman has forgotten that he is also the government spokesman," the state television reporter quipped sardonically.
Elham has also been under pressure after parliament introduced a bill proposing that members of the Guardians Council, Iran's hardline vetting body, cannot hold posts in the government.
"After my appointment as minister of justice and especially as government spokesman, criticism by some critical anti-government media, including state broadcasting, and some MPs, has intensified," he said.
"This has created doubts in people's minds," he added.
Although Elham was quoted as saying last week Economy Minister Davoud Danesh Jaafari and Interior Minister Mostafa Pour Mohammadi were set to step down, their resignations have still not taken place.
The decision to replace the key ministers — which would be the ninth changes to the Ahmadinejad cabinet since he came to power in 2005 — have been sharply criticised in the media and by MPs.
Ahmadinejad cancelled a planned televised interview late Sunday on the economy at the last minute, media reports said, amid speculation he be considering reversing the reshuffle plans.
