Kolkata: Firing a fresh salvo at the Modi government on the Rafale aircraft deal, the Congress on Saturday accused it of ignoring the defence procurement procedure and keeping senior ministers in the dark about the negotiations, demanding a public debate and detailed inquiry into the "secretive" happenings.

Senior party leader P. Chidambaram, while addressing a media conference here, alleged that the price for the aircraft had gone up more than three times under the Bharatiya Janata Party-led National Democratic Alliance (NDA) regime than what was agreed to by the erstwhile United Progressive Alliance (UPA) government.

We think the matter is serious enough that there should be a public debate and a detailed inquiry, which is why the Congress President (Rahul Gandhi) and the party have raised the issue, he said at the West Bengal Pradesh Congress headquarters here.

Chidambaram said the UPA government had entered into a contract to acquire 126 Rafale aircraft -- 18 of them in fly away condition and the remaining 108 aircraft to be made in India by Hindustan Aeronautics Limited in Bengaluru, under a transfer of technology agreement with a French company, Dassault Aviation.

"The negotiated price was Rs 526 crore per aircraft. Suppose instead of 18 aircraft, we were buying 36 aircraft at Rs 526 per aircraft, it would have come to Rs 18,940 crore," he said.

However, after the UPA was voted out in 2014 and the NDA came to power, Prime Minister Narendra Modi during his official visit to France on April 10, 2015, announced that an agreement has been signed to buy off the shelf 36 Rafale aircraft.

Although the price was not revealed, in subsequent documents of Dassault Aviation's report, the price was revealed to be 7.5 billion euros, equivalent to Rs 60,145 crore, Chidambaram said.

The price which was agreed on the Prime Minister's visit was Rs 60,145 crore and per aircraft it comes to Rs 1,670 crore as against Rs 526 crore (negotiated by the UPA), he claimed.

"If these numbers are correct, will someone explain why the price has gone up three times? That is the first question. To which the answer (given by the NDA government) is: 'this is a secret agreement, and we cannot reveal the price'."

"I am revealing the price today, what is so secret about it? It is there in Dassault's annual report which is 7.5 billion euros, which works out to Rs 61,000 crore, and per aircraft it Rs 1,670 core," he said.

Raising questions about the procedure followed to enter into the new agreement, the Congress Working Committee member said: "There is a defence procurement procedure which was completely bypassed. There is a contract negotiation committee, which never met for this deal. There is a price negotiation committee, which was never called to meet for this deal."

"Above all, there is a cabinet committee on security, which has to approve any defence purchase of this size. None of these committees were involved. None of the ministers knew about it. The defence, finance and external ministers did not know about it," he alleged.