More than 50 Bollywood filmmakers, actors and writers have urged Indians not to vote for the opposition Bharatiya Janata Party (BJP) leader, Narendra Modi, in the ongoing parliamnetary elections.
The group signed an appeal calling on Indians to choose a "secular" party, without naming Modi's BJP, on Wednesday.
Critics fear the BJP could stoke religious tensions if it comes to power.
The letter, endorsed by directors Imtiaz Ali, Mahesh Bhatt and Zoya Akhtar, actress Nandita Das and singer Shubha Mudgal, comes as the BJP is tipped to win the biggest share of votes in the election, with Modi becoming the next prime minister.
"The best thing about our country is its cultural diversity, its pluralism, the co-existence of a number of religions and ethnicities over centuries, and hence the blooming of multiple streams of intellectual and artistic thought," the letter said.
"And, this has been possible only because Indian society has prided itself on being essentially secular in character, rejecting communal hatred, embracing tolerance. Today, that very sense of India is vulnerable," it read.
The letter, which appeared on the website of Mumbai Mirror newspaper, called on Indians to vote for the secular party most likely to win in their constituencies.
Protection of India's secular status has surfaced as a key election issue.
Critics fear Modi's nationalist rhetoric could fuel religious tensions in the Hindu-majority country where 13 percent of the 1.2-strong billion population is Muslim.
Modi, the chief minister of the western Gujarat state, remains a divisive figure. He is accused of failing to curb anti-Muslim riots in his state in 2002 in which at least 1,000 people were killed - a charge Modi keeps denying.
Last week, a group of Indian artists and academics, including author Salman Rushdie, wrote to Britain's Guardian newspaper to express "acute worry" over Modi becoming prime minister.