Beppe Grillo, whose anti-establishment party unexpectedly captured a quarter of the vote in Italy's inconclusive elections, wants to renegotiate his crisis-hit country's debt.
"We are being crushed - not by the euro but by our debt," the comedian-turned-populist firebrand told German weekly Focus.
"When [public debt] interest payments reach €100 billion (HK$1 trillion) a year, we're dead. There are no alternatives" to debt renegotiation, Grillo was quoted as saying.
Grillo, 64, leader of the Five Star Movement, said Italy's political system had "only six months" left before it collapsed and the state could no longer "pay pensions and public sector salaries".
If the debt obligations did not change, Grillo said he would want recession-struck Italy to leave the euro and return to the lira, the magazine said.
Drawing a comparison with the private market, Grillo said: "If I've bought shares in a company that goes bankrupt, that's my bad luck. I took a risk, and lost."
With Italy scrambling to find a way out of the political impasse after last weekend's polls, Grillo could become kingmaker after his rogue party drew many austerity-weary Italians to its ranks.
But the party has spooked Europe with its pledge to hold a referendum on the euro and cancel Italy's debts. European leaders have urged Italy to stick to its fiscal commitments and form a government as soon as possible.
Grillo has so far refused to form a coalition with Pier Luigi Bersani, whose leftist party came out on top in the elections, nor with ex-premier Silvio Berlusconi's conservatives.
Grillo has demanded that several conditions be met, including electoral reform and term limits for legislators.