Mr Prodi’s Union coalition won 19,002,598 votes in the lower house to 18,977,843 for outgoing Prime Minister Silvio Berlusconi’s House of Freedoms coalition, the Corte di Cassazione said.
Official confirmation of the Senate vote, which the centre-left won by a two-seat majority, is still awaited by individual courts of appeal within the coming days.
Italian politics had been in a state of suspended animation for nine days since the election, which provisional results had shown the centre-left winning by a razor-thin margin.
Mr Berlusconi, Italy’s richest man, had steadfastly refused to concede defeat, crediting Mr Prodi’s narrow poll win to “irregularities,” and insisting the supreme court review contested votes.
Mr Prodi’s new government, which will include moderate Catholics, Communists and liberals from his multi-hued Union coalition, is set to assume power in mid-May.
The new parliament, which convenes on April 28, must first elect a new state president to replace the outgoing 85-year-old Carlo Azeglio Ciampi, whose seven-year term ends on May 18.
The new Italian president’s first task will be to swear-in Romano Prodi’s government.
Mr Prodi, a 66-year-old former European Commission president, faces an uphill task of putting together a durable government capable of sending a strong signal to the markets and kickstart a stagnant economy, analysts said.
Economists said Mr Prodi will likely appoint a leading financial expert as economy minister, rather than a career politician from within the coalition, a gesture designed to win immediate support from international markets.
Among the front runners are Tommaso Padoa-Schioppa, a former board member of the European Central Bank, and Mario Monti, a former European Competitions Commissioner.
Analysts are worried that the centre-left win is too narrow, and that together with the potential for inter-party differences, badly needed reform will be difficult to achieve.
In the short term, Mr Prodi and his new government face a difficult time on the domestic front, with administrative elections due on May 28 and a potentially divisive referendum in late June on legislation introduced by the Berlusconi government to grant greater devolved powers to Italy’s regions.