During the UPA regime, Sonia Gandhi took oath first as Leader of the House. At that time the Prime Minister Manmohan Singh was a member of the Rajya Sabha and was also Leader of the House.
Former Lok Sabha Secretary General Subhash Kashyap says there is no hard and fast rule on the sequencing of oath taking by members and by convention the Prime Minister takes oath first as Leader of the House.
Today Prime Minister Modi took oath first, then panel Chairman followed by ministers and then Members of Parliament in alphabetical order of the states they represent.