Only 1,411 of the big cats are now left in the country, compared to an estimated 3,500 in the previous survey taken in 2002, the Press Trust of India reported quoting the government.
The census, however, said the 2002 survey may not have been accurate as it was based on pug marks which resulted in some errors.
"This time we have used new and additional methods for tiger census," Rajesh Gopal, secretary of the National Tiger Conservation Authority, was quoted as saying.
Gopal said the depletion in the past five years was so alarming the country no longer has any animals outside of its tiger reserves.
Last month, the government announced it will extend its "Project Tiger" conservation plan for another five years with a $150 million allocation.
The money will be used largely to rehabilitate people living in critical tiger habitat and to set up eight new tiger reserves.
India, once home to half of the world's tiger population, has lost the magnificent animals due largely to poaching or urban encroachment of tiger habitat. A century ago, the country had more than 35,000 tigers.