Standard & Poor's downgraded Italian debt Monday evening to A/A-1 with a negative outlook, warning of the county's weakening economy and precarious debt situation.

"In our opinion, the measures included in and the implementation timeline of Italy's National Reform Plan will likely do little to boost Italy's economic performance, particularly against the backdrop of tightening financial conditions and the government's fiscal austerity program," S&P said in a statement.

Also justifying the unexpected action, the ratings agency cited a fragile governing coalition as a reason for the downgrade.