The Australian has reported that the French builders of India’s six Scorpene-class submarines, DCNS, have suffered a massive leak of secret documents, detailing the entire secret combat capability of the six submarines designed for the Indian Navy.

According to the report, 22,400 pages of documents have been leaked and were marked “Restricted Scorpene India”. “The DCNS documents ­detail the most sensitive combat capabilities of India’s new $US3 bn ($3.9bn) submarine fleet and would provide an intelligence bonanza if obtained by India’s strategic rivals, such as Pakistan or China,” the report adds.

The leaked DCNS data details the secret stealth submarines, including what frequencies they gather intelligence at, what levels of noise they make at various speeds and their diving depths, range and endurance, where the submarine crew on the boat can speak safely to avoid detection by the enemy, magnetic, electromagnetic and infra-red data as well as the specifications of the submarine’s torpedo launch system and the combat system.

“It details the speed and conditions needed for using the periscope, the noise specifications of the propeller and the radiated noise levels that occur when the submarine surfaces,” The Australian reported.

DCNS has however hinted that the data leak could have happened at an Indian sub-contractor’s end.

The sea trials for the first of India’s six Scorpene submarines began in May and the project is running four years behind schedule, according to the report.