Chetan Bhatt, a professor of sociology at the London School of Economics and a signatory of the letter, added: "Modi perfectly embodies a callous, dangerous and authoritarian ideology that stands opposed to genuine liberal, democratic and secular values that founded the modern state of India."
Senior officials of the BJP reacted angrily to the open letter.
"These comments are prejudiced, biased and some of these people have entertained a pathological hatred towards Mr Modi for years," said Ravi Shankar Prasad, deputy leader of the party.
"The BJP has grown in spite of their opposition for so many years and the Left has gone down in spite of their support because the people of India trust in Mr Modi and the BJP to save India from all ills that India is suffering," he said.
