Amid opposition criticism of the viability of the project, a Mumbai-based activist, Anil Galgali, had asked for details of the Mumbai-Ahmedabad train route and the railways' revenue from July 1 to September 30.

No new trains are being planned for the route, say railway officials. The Shatabdi Express, which is the most preferred train, also managed to sell only half its seats on the route over the last three months.

Most passengers are travelling on sleeper trains but many upper class seats are going unsold, according to officials.

Last month, PM Modi, along with Japanese Prime Minister Shinzo Abe, launched the Rs 1.10 lakh crore project, calling the bullet train a "giant step in fulfilling a long cherished dream".

The bullet train, using Japanese trains and technology, will cut the 500 km journey between Gujarat's Ahmedabad and Mumbai, India's financial capital, from eight hours now to just over three hours.

The new train will have a capacity to carry 750 passengers. It has a top speed of up to 350 kilometres an hour -- more than double the maximum speed of the fastest ones in India today.

The Railways ministry is collaborating with Japan's Shinkansen Technology for the train. Japan, which is providing 85 percent of the cost in soft loans, will also facilitate transfer of technology through training of local engineers.

The Congress has been one of the loudest critics of the bullet train project, calling it an example of the government's "misplaced priorities".

Nationalist Congress Party chief Sharad Pawar had also questioned the wisdom of the high-speed train between Ahmedabad and Mumbai, calling it "impractical".