France and India have played down the security risk posed by leaked data on French-designed submarines that a source says was probably stolen by a French former employee and that has raised concerns over a $A50 billion contract with Australia.
More than 22,000 pages of data about six submarines that France's DCNS is building for India's navy looked to have been stolen in 2011 by a subcontractor who was fired while providing training in India, the source said on Thursday.
India's defence ministry said on Thursday it saw no immediate security risk and the French government said the information in the documments only showed how the submarines operate and did not compromise their security.
India and France are investigating after The Australian newspaper published on Wednesday details about its Scorpene submarines being built by French contractor DCNS - 35 per cent owned by Thales and 65 per cent by the French state.
"It is not a leak, it is theft," the source said. "We have not found any DCNS negligence, but we have identified some dishonesty by an individual."
The French government source said security procedures would be strengthened for all employees going to work in Australia to ensure one person did not have access to so many documents.
The documents were not classified and at this stage appeared to only focus on how the submarines are operated not how they are built and whether they can be detected, the source said.
"The Indians can object to the fact that these documents show the Pakistanis how to maintain their submarines and that's annoying, but it doesn't tell the Pakistanis how to detect an Indian ship, or how we build a submarine in France. Not at all," the source said.
The newspaper published only a fraction of the documents, and these had been redacted, meaning that sensitive details relating to the Scorpene's design and stealth capabilities did not enter the public domain.
"The documents that have been posted ... have been examined and do not pose any security compromise as the vital parameters have been blacked out," an Indian defence ministry statement said.
The submarines are being built at a state-run shipyard in Mumbai. The first is expected to enter service by the end of the year as India seeks to rebuild its dwindling fleet and assert its dominance in the strategic waters of the Indian Ocean.
The leak has raised doubts about the security of a separate DCNS submarine project in Australia where it is locked in exclusive negotiations after seeing off rivals on a contract to build the Barracuda next generation of submarines.
DCNS said it was working to determine if any harm had been caused to clients and whether commercial espionage was to blame.
DCNS is also pitching for submarine contracts in Norway and Poland and beat Germany's ThyssenKrupp AG and a Japanese-government backed bid by Mitsubishi Heavy Industries and Kawasaki Heavy Industries for the Australian contract.
French officials have sought to play down the impact on the Australia contract.
"The dialogue with Australia has not been cut at all. There is mutual confidence and I don't believe at all that this contract will be put into question," said Patricia Adam, the head of France's parliamentary defence committee.
