"I had decided on this before becoming the Prime Minister. Few exceptions aside, I won't take part in inauguration ceremony or programmes," Pushpa Kamal Dahal 'Prachanda' said at a programme in Banasthali.
"Constitution implementation, reconstruction and economic reforms are on the priority list of his government," he said.
The CPN (Maoist Center) chairman also claimed his party would become the biggest party after unification among 10 Maoist parties.
He was Prime Minister from 2008 to 2009 before a disagreement with the President over his attempt to sack the army chief brought his period in office to an early end.