The development came a day after the government appointed Vice Chief of Army Staff Lt Gen Bipin Rawat as the new army chief superseding his two senior officers.
Congress spokesperson Manish Tewari said that every institution has its own dynamics, hierarchy and seniority which is the overriding dynamic of the armed forces not only in India but everywhere in the world.
"With all due respect to Gen Rawat's professionalism and no personal animus towards anybody, there is a legitimate question that why has that supersession taken place," he said.
Arguing that Eastern Army Commander Lt Gen Praveen Bakshi and Southern Army Command chief Lt Gen P M Hariz are senior to Lt Gen Rawat, Tewari questioned why this supersession has taken place.
He said now the argument the government will give that Congress did supersession in the 80s and, therefore it has the right to do so is a "complete nonsense".
"Every situation has its own context and, therefore nothing can be extrapolated out of context in order to justify a supersession. So, therefore the government needs to answer this legitimate question as to why these senior army commanders were superseded," he said.
"Did the government have anything against them? Was their professionalism in question? What was the reason and I guess the army being a public institution the country deserves those answers," Tewari said.
CPI leader D Raja also questioned the government's move and said appointments have become controversial.
"Appointments in the army have become controversial, the appointments in the judiciary are already controversial, the appointments of CVCs, CBI director and to Central Information Commission, all these top-level appointments are becoming very controversial," he said.
Terming this as "very unfortunate", Raja said it is not in the interest of democracy and the country.
He said there should be transparency and transparency should go along with integrity and nobody should raise questions. "But now questions are being raised," he added.
Government justifies Lt. Gen. Rawat as next army chief
The Defence Ministry insisted on Sunday that Lt. Gen. Bipin Rawat, named the next Army Chief overlooking the generally followed seniority norm, was "best suited" for the job.
The appointment of Lt. Gen. Rawat has ignored the seniority of Eastern Army Commander Lt. Gen. Praveen Bakshi and Southern Army Commander Lt. Gen. P.M. Hariz who have spent longer years in service.
Lt. Gen Bakshi was also not appointed the Vice Chief when the post fell vacant in September and Lt. Gen. Rawat was brought in from the Southern Command.
"He was found the best suited among the Lt. Generals, to deal with emerging challenges, including a reorganized and restructured military force in the north, continuing terrorism and proxy war from the west, and the situation in the northeast," a source in the ministry said.
On Friday, asked if the line of succession will be broken, Defence Minister Manohar Parrikar had cryptically remarked: "Line of succession is decided by the people."
Lt. Gen. Rawat was commissioned in the Fifth Battalion of the 11 Gorkha Rifles in December 1978 from the Indian Military Academy (IMA), Dehradun, where he was awarded the 'Sword of Honour'.
He has commanded an infantry battalion along the Line of Actual Control (LAC), a Rashtriya Rifles Sector and an infantry division in the Kashmir Valley.
He also has vast experience in high altitude warfare and counter insurgency operations.
"Lt. Gen. Rawat has tremendous hands on experience of serving in combat areas and at various functional levels in the Indian Army over the last three decades," said the source who did not want to be named.
"He has handled various operational responsibilities in many areas, including along the LoC (Line of Control) with Pakistan, LAC with China and in the northeast," the source said.
"He is known for his balanced approach towards soldiering, compassion, and connect with civil society. His experience as GOC-in-C (general officer commanding-in-chief) Southern Army Command in Mechanised Warfare has been focused towards the western borders, in coordination with the other two services," the source added.
Soon after the appointment was announced, the Congress questioned the government decision.
Congress leader Manish Tewari tweeted: "Why has seniority not been respected in appointment of Army Chief? Why have Lt. Gen. Pravin Bakshi and Lt. Gen. Mohamed Ali Hariz been superseded, Mr PM (Narendra Modi)?"
The Defence Ministry on Saturday night announced the names of the next chiefs of Army and Indian Air Force, 13 days before General Dalbir Singh and Air Chief Marshal Arup Raha are to retire.
Air Marshal B.S. Dhanoa will be the next chief of IAF.
Commissioned into the IAF's fighter stream in June 1978, Dhanoa, who has flown various types of fighter aircraft and is a qualified Flying Instructor, commanded a fighter squadron during the Kargil Operations and flew numerous night strike missions in the mountainous terrain.
He has also held a number of important operational appointments including commanding a fighter base and leading the Indian Military Training Team in Bhutan.
He has also served as Chief Instructor (Air) at the Defence Services Staff College, Wellington, Assistant Chief of Air Staff (Intelligence) and Senior Air Staff Officer (Chief of Staff) of two operational commands.