The Congress president also said that it was "for the first time" that the country's defence minister (Nirmala Sitharaman) was not sharing the purchase price of the aircraft as he asked the media why it was not raising questions on the issue.
"Top Secret (Not for Distribution)/the defence minister says the price negotiated for each Rafale jet by the prime minister and his 'reliable' buddy is a state secret," he tweeted, without naming the "reliable buddy".
Gandhi's attack came a day after Sitharaman refused to share the details of the deal on the grounds of security agreement signed between India and France in 2008.
Her response was to a written question in Rajya Sabha by Samajwadi Party member Naresh Agrawal, who had asked whether the government did not want to disclose in public domain the agreement between India and France for purchasing the aircraft.
"And the defence minister is saying she will not inform India, the Indian martyrs and their relatives about the money spent on buying those aircraft. What does this mean? This only means there is some scam," he alleged.
Gandhi said he had raised the issue during the Gujarat assembly polls as well.