ROME - More than a third of Italy's population will be over 65 by 2050, up from about a quarter last year, the country's statistics office ISTAT said on Thursday, offering more evidence of a serious demographic crisis.

In a report, ISTAT also estimated that the ratio between people of working age (15-64) and people who are too young or too old to work (0-14 or 65 and above) "will decrease from about three to two in 2022 to about one to one in 2050."

A shrinking and ageing population is a major worry for the euro zone's third-largest country, leading to falling economic productivity and higher welfare costs in a country with the highest pension bill in the 38-nation Organisation for Economic Cooperation and Development (OECD).

According to ISTAT, Italy's population is set to decline to 54.4 million people by 2050 from 59 million in 2022, when births dropped to a new historic low of under 400,000.

Prime Minister Giorgia Meloni's government has made it a priority to tackle the issue since taking power last year, pledging to provide more support to families who want to have children.

Meloni also said this month she does not believe that immigration can be a solution to the demographic crisis affecting Italy and the rest of Europe.

Italy's school population will shrink by one million in the coming decade because of plunging birth rates and continuing brain drain, Education Minister Giuseppe Valditara said in May, calling it an "alarming" scenario.

(Reporting by Antonella Cinelli, editing by Alvise Armellini and Anil D'Silva)