The level was 0.3 percentage points higher than over the same period in 2012, Istat said.
Italy last year exited the EU's excessive deficit procedure for countries which breach the limit of 3.0 percent of GDP.
Italy's primary balance, before interest on debt is counted, was however in surplus in the third quarter at 1.8 percent of GDP – 1.6 points higher than in 2012.
Italy has vowed to remain below the EU-mandated 3.0-percent for 2013 as a whole.
But the European Commission has voiced concern about the rapid increase in public debt in Italy, the eurozone's third largest economy, which is due to reach a record-high of 134 percent of GDP this year.