[5] He was once the designated successor to the revolution's Supreme Leader, Ayatollah Khomeini; they had a falling-out in 1989 over government policies that Montazeri claimed infringed on people's freedom and denied them their rights, especially after the 1988 mass execution of political prisoners.

Montazeri spent his later years in Qom and remained politically influential in Iran but was placed in house arrest in 1997 for questioning "the unaccountable rule exercised by the supreme leader",[6] Ali Khamenei, who succeeded Ruhollah Khomeini.

While there he answered Khomeini's call to protest the White Revolution of Shah Mohammad Reza Pahlavi in June 1963 and was active in anti-Shah clerical circles.

He was the author of Dirasāt fī wilāyah al-faqīh, a scholarly book advocating the supervision of the administration by Islamic jurists.

[18] Later, Montazeri relented, and following a session of the Assembly of Experts in November 1985, he was officially appointed Khomeini's successor as Supreme Leader.

[11]In addition, traditionalists did not approve Montazeri's designation as successor due to several reasons, including his problematic persona in Shiite seminaries during the reign of the Shah and his support for Ali Shariati’s and for Nematollah Salehi Najaf Abadi's works.

"[26] Things came to a head following the mass execution of political prisoners in late summer and early autumn 1988, when Montazeri gave a series of lectures in which he indicated support for a "far more open" policy.

"[32] In addition to losing his position as designated heir, Montazeri's title of Grand Ayatollah was withdrawn, publication of his lectures in the Kayhan newspaper and references to him on the state radio were stopped, his portraits were ordered by the then Prime Minister Mir Hossein Mousavi to be removed from offices and mosques,[33] and his security guards were withdrawn.

[34] According to numerous sources, the amendment to Iran's constitution removing the requirement that the Supreme Leader be a Marja was instituted to deal with the problem of the lack of any remaining Grand Ayatollahs willing to accept "illimitable velayat-e faqih".

[37][38] Khomeini died in June 1989 and another cleric, Seyed Ali Khamene'i, was selected by the Assembly of Experts to be the new Supreme Leader.

In December 1989, Montazeri's supporters in Qom distributed "night letters" questioning Khamenei's qualifications to be a Marja e Taqlid ("Source of Emulation"), or in other words, an Ayatollah.

"[18] In October 1997, after openly criticizing the authority of Khamenei, Montazeri was placed under house arrest under the pretext of protecting him from hardliners.

Some thought that the government lifted the house arrest to avoid the possibility of a popular backlash if the ailing Montazeri died while in custody.

[44] Montazeri also criticized Iran’s economic performance under Ahmadinejad's administration, noting the rate of inflation—including a 50% increase in housing costs[44]—and arguing that a country cannot be run on "slogans".

[50][51] In November 2009, on the day before the 30th anniversary celebration of the Iran hostage crisis, Montazeri said that the occupation of the American embassy in 1979 had been a mistake.

When we say humans, it includes both men and women... you see, if people around the world want to say certain things about women for example being equal to men in matters of inheritance or legal testimony, because these issues pertain to the very letter of the Qur'an, we cannot accept them... Now, consider that God Almighty has made it incumbent upon men to cover the expenses of women... in Iran we cannot accept those laws that are against our religion... on certain occasions that these laws contradict the very clear text of the Qur'an, we cannot cooperate... Men in general (no'-e mard ha), all things considered, are productively more active—both intellectual activities and practical activities... All things considered, the intellectual and practical activities of men are more than women.When Bashi informed him that currently (2003) in Iranian universities, "some 60% of students are women" and asked him "so in future generations, when the number of professors, physicians, high-ranking experts, etc, will be mostly women, will Islam be able to have an ijtihad and modify these unjust laws because they no longer correspond with reality?

Montazeri's detractors portrayed him as stubborn and naïve in his insistence that the Islamic republic find reconciliation with the "hypocrites" and "liberals" who are its "internal enemies.

"[8] In late 1960s, Montazeri gained influence and popularity in Isfahan Province after his speeches criticizing the Shah, moving SAVAK to banish and subsequently imprison him.

According to Elaine Sciolino, this was due to his "poor public speaking skills, squeaky voice, round face and grizzled beard".

[62] After the special prayers by Ayatollah Mousa Shabiri Zanjani,[63] his body was laid to rest in the Fatima Masumeh Shrine.

Spent on the Basiji,” and “Basij’s great pride, rape in prison.”[67] On the same day, Mir-Hossein Mousavi stepped out from the compound of Grand Ayatollah Saanei, a fellow reformist, to cross the street to Montazeri’s house in Qom.

When a crowd of pro-government supporters chanted back: "I will give my life for the supreme leader," they were booed by mourners, a witness said.

[50] The security forces prevented the Ayatollah's family from holding a planned memorial ceremony in the grand mosque of Qom following the funeral.

[68] According to the reformist website Kalameh, men on motorbikes, believed to be Ahmadinejad supporters, attacked the car carrying Mir Hossein Mousavi back from Qom to Tehran.

He interrupted a visit to Shiraz to return to Tehran and remove Mir Hossein Mousavi, the main opposition leader he defeated in the presidential election, as head of the state Academy of Arts and Culture- a post he had held for ten years.

Activists said police used tear gas, pepper spray and batons to disperse people gathering to commemorate Grand Ayatollah Montazeri in the Seyed mosque.

People had gathered at the main mosque for the memorial service, but when they arrived the doors were closed and security forces told them to leave.

Security forces also sealed off the home of Ayatollah Jalal Al-Din Taheri, who organised the service and used to lead Friday prayers in Isfahan until he resigned in 2002 in protest at the government’s growing authoritarianism.

[76] On 24 December, opposition web sites reported that police in Tehran and the northwestern city of Zanjan clashed with protesters defying an order by the Iranian government banning memorial services for Montazeri.

[77] Witnesses and opposition websites reported the following incidents: In 2010, the office of Montazeri that had been run by his son Ahmad was closed on the orders of Ali Khamenei.