A report by India's Times News Network said Mazagon Dock Ltd., the government shipbuilder in Mumbai where the vessels are being made, informed the navy that the project would be delayed by another 18 months to the end of 2016.
Last year Defense Minister A.K. Antony announced in Parliament that the project would be delayed three years until 2015.
The Scorpene is a diesel-electric attack submarine with additional air-independent propulsion jointly developed by the French shipbuilder DCN -- now DCNS -- and Spain's Navantia.
The submarines were ordered in 2005 under a technology transfer agreement.
The 219-foot-long vessel has a speed of more than 20 knots with a displacement of 1,700 tons. With a crew of 31, it can remain at sea for about 45 days and can dive to depths of more than 1,000 feet.
India's Ministry of Defense approved the six-vessel submarine purchase strategy in 1997 and the go ahead for construction of the subs in September 2005 at a cost of nearly $3.45 billion.
The cost had risen to $4.3 billion by February 2010, a recent Press Trust of India report said.
But this week TNN reported the exit of Navantia after a technical assistance agreement expired at the end of last month. Ten Spanish consultants left India, meaning more delays could ensue, unnamed sources said.
Management personnel from Mazagon are expected to meet with the government to demand additional funds for technical assistance, TNN said.
Delays will put operational pressure on India's submarine fleet of 10 aging Russian Kilo class and four German HDW submarines. India also leases a Russian nuclear submarine, Chakra.
Three of the subs are expected to be retired in the next several years.
TNN said the hulls for all six Scorpene submarines, made of steel supplied by French division of ArcelorMittal, are ready in Mumbai and Mazagon is tooling up of shipbuilding equipment and systems.
But the Spanish consultants were heavily involved in the hull work, meaning their departure likely will affect production.
The original Scorpene contract came under intense scrutiny by the government's public accounts committee, which said the deal gave "undue favor to the vendor," resulting in a financial loss to the government.
A report this week by the Press Trust of India quoted France's ambassador to India saying the first submarine would be delivered by 2014.
Delivery of the first sub will be a "strategic tie-up" for both countries, French Ambassador Francois Richier said during a trip to the western port of Goa.
Richier was visiting the French destroyer Montcalm on training exercises with the Indian navy.
"The submarines are important for the Indian navy considering the long coast it has to guard," he said.