Politicians and interest groups championing low-caste Hindus and other marginalised groups that the system is designed to help have come out in force against "Aarakshan" (Reservation), which hits screens today.
Two north Indian states -- Uttar Pradesh and Punjab -- have even banned the film, with the Uttar Pradesh government, led by low-caste politician Mayawati, saying it "could incite civil disorder and violence".
Critics, including the National Commission for Scheduled Castes, have said Prakash Jha's drama contains "objectionable" references to marginalised groups such as Dalits, the community formerly known as "untouchables".
The ban in Uttar Pradesh, announced late Wednesday, will last two months while Punjab will decide whether to show the film only after a state government panel has reviewed it, officials said on Thursday.
"Aarakshan", which sees screen legend Amitabh Bachchan play the principal of a successful school who has quotas imposed on him, was dogged by controversy even during shooting.
Dalit groups opposed the casting of Saif Ali Khan, who is of Muslim royal stock, as a low-caste Hindu. And the film's set in Bhopal, central India, was deemed illegal and bulldozed.
Publicity material was vandalised and more than a dozen activists arrested for protesting outside Jha's office in Mumbai last weekend, prompting police to give him and the lead actors extra security.
India's Censor Board, which passed the film uncut, has been asked to look at it again.
Jha, known for tackling social issues in his films, denies taking a position on reservation and Dalit rights.
"In India there are people who benefit from this policy and there are those who have missed an opportunity because of the policy. Reservation and the quota system is a hard-hitting reality," he said last week.
"It is almost an India versus India situation and by showing this in my movie, I am trying to bridge the gap."
Reservation refers to the policy of guaranteeing jobs for socially disadvantaged groups, officially referred to as "scheduled tribes, scheduled castes and other backward classes".
The affirmative action aims to provide equal opportunities for the poorest and most marginalised in India's complex and deeply entrenched social hierarchy.
India's 160 million Dalits, many of whom live in rural areas, still face prejudice despite anti-discrimination laws, while harsh retribution is often meted out for flouting caste and sub-caste lines.
The quota system itself is the subject of frequent challenges, with the number of places allocated to disadvantaged groups changing from state to state and sometimes exceeding the legal maximum of 50 percent.
Those who miss out on public sector jobs or education places as a result say the system fails to reward talent or ability.
Some sociologists have suggested that traditional caste notions have been eroded in any case due to India's economic boom, improving wealth and social mobility.
Professor Kamal Mitra Chenoy, a political scientist at Jawaharlal Nehru University in New Delhi, said the phenomenon was more noticeable in fast-growing cities but the pace of change was slow.
"It's still a major issue," he said but admitted that given the chronic under-investment in state education there was "no alternative" to quotas apart from a concerted government drive to lift millions out of poverty.
Other Bollywood films have faced protests in recent years, most notably Deepa Mehta's "Fire" (1996), for its portrayal of lesbianism, and "Water" (2005), about the treatment of widows in Indian society.
Critics of actor Shah Rukh Khan's support for Pakistani cricketers threatened to disrupt showings of his film "My Name Is Khan" in 2010.
But the objections have mainly been against sex or nudity on moral grounds from conservative Hindu groups, who see themselves as champions of traditional Indian values.
For his part, Jha has accused politicians of playing communal politics in the quest for votes.
"I am just trying to show how it (reservation) has created two Indias," he said. (AFP)
