The statue of Chhatrapati Shivaji, a 17th-century Hindu ruler who fought the Muslim Mughal dynasty and carved out his own kingdom, will be more than twice the size of the Statue of Liberty and five times higher than Christ the Redeemer in Rio de Janeiro.
The structure, a pet project of Hindu nationalist Modi, will rise 192 metres (630 feet) from an island off the western coast of Mumbai in the Arabian Sea.
When finished, it will tower over the 128-metre Spring Temple Buddha in China's Henan province that is currently the world's tallest statue.
The government of Maharashtra state, of which Mumbai is the capital, is expected to spend some 36 billion rupees ($740 million) on the statue, which is scheduled for completion by 2019.
By Saturday evening, more than 27,000 people had signed an online petition on Change.org urging the government to drop the plans.
