ARERA, which sets regulated gas prices for Italian consumers, also said the price for December rose 23.3% from the previous month, reflecting high prices in early December before a dip later in the month.
An average family would have spent around 1,866 euros ($1,968.63) on gas last year, it estimated.
Marco Vignola, who speaks on energy issues for the National Consumers' Union, said the prices "were unsustainable for too many Italians" and urged the government to do more to help.
The Italian budget for the coming year has earmarked over 21 billion euros to help firms and households pay electricity and gas bills, mainly through subsidies for energy-intensive firms and low income families.
ARERA late last year started setting regulated gas prices on a monthly rather than quarterly basis due to market uncertainty related to gas supplies on the back of the war in Ukraine.
European Union countries agreed in December to cap gas prices to try to limit further rises on the market, which hit record levels in Europe after Russia's invasion of Ukraine led to the disruption of supplies.
($1 = 0.9479 euros)
(Reporting by Francesca Landini and Keith Weir; editing by Barbara Lewis)
