Taking to Twitter, Chidambaram said the Air Force wanted at least seven squadrons (126 aircraft) and this figure was recommended by the Defence Acquisition Council too.
"Did the Air Force or the DAC ever reduce the requirement to 36 aircraft," he asked.
He said if the price negotiated by the BJP government was cheaper by 9 to 20 per cent, "logically the government should buy more aircraft. Why is it buying less number of aircraft?"
"The BJP says it was an emergency purchase. The PM's statement in Paris was on 10-4-2015. Four years have passed, not one aircraft has arrived in India until this date. Some emergency purchase!
"We charge the BJP government of compromising national security by buying only 36 aircraft when the Air Force's requirement is 126 aircraft. Why did the government not enter into a contract to buy 126 aircraft," he said in a series of tweets.
"To the question why did you reduce the number of aircraft to be purchased from 126 to 36, the Defence Minister says that you would have got 18 aircraft in fly away condition but we will get 36 aircraft in fly away condition. Is that an answer to the question," he tweeted.
In a fiery "point-by-point" rebuttal to Congress's charges on the Rafale deal in Lok Sabha, Defence Minister Nirmala Sitharaman said on Friday it was the Indian Air Force which suggested that the government buy two squadrons or 36 Rafale jets in fly-away condition instead of 18, as was planned to be purchased under the Congress-led UPA government.