The cost of borrowing is at a record high for Italy, despite a deal being reached to contain the eurozone debt crisis.
Italy paid 6.06% to borrow for 10 years at an auction on Friday, the most since the euro was created in 1999.
The rate jumped from 5.86% - the previous record high - at its last auction a month ago.
The Italian Treasury also failed to meet its borrowing target, having hoped to sell as much as 8.5 billion euros ($US12.1 billion) of bonds. Only 7.9 billion euros of 10-year debt was sold.
The BBC reports Italy has the highest total debt in the eurozone, amid stagnant growth. But it has the advantage of having most of its debt owed to its own people rather than external investors.
On Thursday, eurozone leaders on Thursday agreed to expand the single currency's bailout fund to 1 trillion euros and to take measures to recapitalise banks.
