Religious tensions and attacks on freedom of expression have grown under Prime Minister Narendra Modi's administration, Amnesty International said in a report Wednesday.
The human rights group's annual report criticized what it saw as arbitrary arrests, caste-based discrimination, and extra-judicial killings in India.
The report said the Hindu nationalist Bharatiya Janata Party government failed to prevent hundreds of incidents of communal violence, usually between majority Hindus and the minority Muslims.
"Censorship and attacks on freedom of expression by hardline Hindu groups grew. Scores of artists, writers and scientists returned national honours in protest against what they said was a climate of growing intolerance," the report said.
Indian intellectuals protested after the murders of two rationalist writers and killings of four men over rumours of cow slaughter. The cow is regarded as holy by the Hindus.
Modi, who has come under criticism for not taking a strong stand over religiously-motivated violence, has blamed anti-government propaganda and efforts to defame him.
Amnesty also expressed concern over incidents of violence against low-caste groups and tribals, saying 58,000 crimes against these communities were reported in 2014.
The report came as the Indian parliament was repeatedly stalled on Wednesday following opposition protests over the death of a student who faced caste-discrimination.
Also in Delhi, there have been a series of protests by students and opposition parties, accusing the BJP of crushing dissent. Three students have been arrested for sedition over the protests.