Italy had 104 infringement cases out against it at the end of last year, more than five times law-abiding Latvia (20) which took the top spot.
In total there were 472 complaints made against Italy’s failure to properly apply EU law in 2013, according to the European Commission report.
The largest number of these related to employment, with 120 complaints against the state, followed by internet markets & services (81) and the environment (64).
In the latter area, the European Commission has chastised Italy for pollution at the Ilva steel plant in southern Taranto.
The factory, which employs around 1,400 people, is at the centre of a long-standing legal battle in which the owners have been accused of fraud and toxic pollution.
After Italy, Spain was Europe’s second-worst country for applying EU law. There were 439 complaints made against Spain in 2013, with 91 outstanding cases at the end of the year.
Germany had the third highest number of complaints made against it last year - 297 - but by the end of the year all but 63 cases had been resolved. Overall, therefore, Germany stood in seventh place in December, while Greece took third place with 79 outstanding cases.