But there is already some skepticism as to whether the motion will have the key backing of Iran's supreme leader, especially at a time when the country is under increasing pressure over its disputed nuclear work.
Some legislators said earlier they had withdrawn their signatures from the document.
Motahari, who is said to be the architect of the motion, has denied those reports, however, in an interview with "Aftabnews."
"If someone wanted to take back his signature, he should have come to me, up to today not even one person has come to take back his signature," Motahari said.
According to Iran's Constitution, the motion to question the president needs the signature of at least one-fourth of parliament members, or 73 legislators, have to sign the motion.
Motahari says that so far more than 50 legislators have signed it. He said he's the only person who knows the names of the signatories.
Others had reported that about 40 legislators have signed the document.
One pro-government lawmaker had suggested that the signatories would be conservatives who are critical of Ahmadinejad, to be joined by about 25 legislators from the parliament's minority faction.
When asked about when the motion would be presented to the parliament's presiding board, Motahari said that it would take place based on "social and political conditions," adding that until the plan to remove subsidies was implemented and the price of energy was specified, the plan would not be presented to parliament. This suggest that a move against Ahmadinejad could be several months away.
The motion against Ahmadinejad took shape in mid-October after the tensions with the conservative-dominated parliament reached new heights.
One reason was Ahmadinejad's statement that the parliament was not the highest power anymore and that the executive branch was in charge of running the country, while other branches had to support it.
Those comments are among the subjects of the motion, which also includes "lack of attention to the country's cultural problems" and "comments by Ahmadinejad's adviser, Esfandiari Rahim Mashaei, regarding Iranian doctrine instead of Islamic doctrine."
What could be the results of such a move, and could it eventually lead to Ahmadinejad's impeachment? Most analysts agree that the support of Supreme Leader Ayatollah Ali Khamenei is crucial.
Khamenei has invested a lot in his hard-line president, who has turned into one of the most divisive figures of the Iranian establishment, so there is much doubt about whether he would allow any significant move against the president.
Germany-based political analyst Hassan Shariatmadari says a potential impeachment of Ahmadinejad without Khamenei's approval is "impossible."
"Khamenei would express his view in the final moments and it's also possible that he would give some positive signals to [those opposed to Ahmadinejad] to demonstrate his power and authority to the president," Shariatmadari says, "but in the final moments he would most probably take the side of the government."
Over the weekend four lawmakers said in a letter that they had so far refrained from questioning and impeaching the president under "orders" from the supreme leader about the need for the parliament and the government to work together. They accused Ahmadinejad's government of breaking the law and trying to limit the power of the parliament.
The move against Ahmadinejad and the increasing criticism of his actions reflects the deepening fissures within the conservative faction.
The tensions have been mounting over the deteriorating economy, the plan to cut subsidies, and other issues, including Ahmadinejad's increasing power and his controversial aide and his reported attempt to push him as his successor.
A pro-government lawmaker, Mohammad Rasayi, has described the plan to call Ahmadinejad to account as a "political grudge" and predicted that it would lead nowhere.
Motahari himself said that some had created "a taboo" out of the motion against the president, adding, "so we have to be careful about the timing."
Houshang Jeirani of RFE/RL's Radio Farda notes that parliament has been trying to impeach eight of Ahmadinejad's ministers without success, so impeaching Ahmadinejad seems to some a bit far-fetched at this point. But politics in Iran has proven unpredictable before.
The Iranian parliament has only impeached one president in its history: Abolhassan Bani Sadr, who was impeached in 1981 in his absence and removed from power with the blessing of the founder of the Islamic republic, Ayatollah Ruhollah Khomeini.
-- Golnaz Esfandiari