The head of Italy's centre-left bloc has hit an impasse in his efforts to form a government and said only a mentally ill person would want to govern Italy now.
Pier Luigi Bersani was rebuffed by the anti-establishment Five Star Movement on Wednesday.
If he cannot form a coalition, fresh elections could be held in June.
Meanwhile caretaker Prime Minister Mario Monti has said he "can't wait" to leave office.
The political stalemate is delaying reforms that could help revive Italy's recession-hit, debt-laden economy.
Mr Bersani's Democratic Party narrowly won the elections last month but lacks the upper house majority needed to govern.
Five Star, led by former comedian Beppe Grillo, won an unexpected 25% in the election and holds the balance of power.
"Only a mentally ill person could have a burning desire to govern right now," Mr Bersani said at a meeting with Five Star politicians.
"I want things to be clear: I am ready to assume a huge amount of responsibility, but I ask everyone else to take on a little bit themselves," Mr Bersani said.
He has ruled out forming a coalition with the centre-right bloc of former prime minister Silvio Berlusconi, the second largest force in parliament.
Later this week Mr Bersani is expected to report back to Italian President Giorgio Napolitano, who will decide how to proceed.
He has the power to look again to a respected technocrat to try to form an interim government.
Hours after Mr Bersani had suggested that governing Italy at the moment was not perhaps the wisest of moves, caretaker Prime Minister Mario Monti appeared before parliament asserting that his government "can't wait to be relieved of its duty".
Mr Monti was addressing the Chamber of Deputies following the surprise resignation of Foreign Minister Giulio Terzi in parliament on Tuesday.
Mr Terzi said he could no longer be part of the government after it decided to send two Italian marines to face trial in India over the deaths of two fishermen, in a case that prompted a diplomatic row.
Mr Monti - an economist and former EU commissioner - was appointed caretaker prime minister in November 2011.
His austerity measures proved widely unpopular and in last month's election his group came fourth with just 10% of the vote.
Hinting at splits in his caretaker administration, Mr Monti told MPs that the foreign minister was looking at "other goals". His claim was later denied by Mr Terzi on Facebook, Ansa news agency reported.