The European Environment Agency said the debt-ridden countries are not on track to make the emissions cuts required by the Kyoto Protocol, and have not bought enough credits to offset the shortfall.
Such credits allow countries to offset their own emissions through CO2-reducing investments in developing countries.
Though the EU is on track to meet its overall target, its members must also meet their individual goals. In a report Wednesday, the EEA said that current gaps in Italy and Spain, if not addressed through Kyoto credits, could put the EU commitment at risk.
Though Kyoto expires this year, countries can use the offset mechanism until 2015.