'I do not want to live in an illiberal country, governed by immature forces and by men linked closely to a politically and economically bankrupt past,' he said.
Mr Berlusconi, who owns three of Italy's six television channels and one of the biggest magazine and book-publishing empires in Europe, as well as supermarket, insurance, property interests and the cup-winning football team AC Milan, declared he had resigned 'this very day' from all offices he holds in his companies.
'I renounce therefore my role as publisher and entrepreneur to put my experience and all my commitment into a battle in which I believe with absolute conviction,' he said. Italy 'needs people with heads on their shoulders and accumulated experience, people who are creative and innovative, capable of giving a hand and making the state work'. He launched into a diatribe against the former Communists, whom he claimed had not really changed, and appealed to viewers to 'get involved yourselves, all of you, now, immediately, before it is too late . . . I tell you we can, we must build together, for ourselves and our children, a new Italian miracle'.
Mr Berlusconi had teetered on the brink - or as the Milan chairman himself put it, 'warmed up on the touchline with my tracksuit still on' - for weeks in the hope, he said, that the centre-right groupings would form a united front. At present the left-wing groups, which appear relatively compact, look likely to win the 27-28 March elections.
But despite ultimatums from the tycoon, the various groupings, ranging from the centrist Popular Party - the bulk of the old Christian Democrats - through to the neo-fascist National Alliance, have so far been failed to get organised. An agreement on a government programme reached between the electoral reformer Mario Segni and the Northern League at the weekend lasted only a couple of days.
Whether Mr Berlusconi's arrival in the field will help remains to be seen: the first reactions to his long-expected announcement were distinctly chilly. More likely he and his political movement Forza Italia, which espouses Thatcherite economic policies and 'family' values, will simply add to the already large range of centre-right groupings.
His move, the middle-of-the-road Corriere della Sera newspaper commented yesterday, was a symptom of the 'total chaos' in centre-right ranks. 'This move therefore will not solve in any way the problems he proposes to solve, nor will it succeed in ushering in anything new.'
He will bring to the right, however, highly professional, American-style campaign techniques which are badly lacking, particularly among the new and inexperienced political groupings. His Forza Italia, which echoes the soccer fans' cry 'Come on, Italy' but could also mean Italian Strength, is already a nationwide network of clubs and candidates, backed by a slick opinion-poll and marketing operation and know-how and training for candidates.
His resignation from executive office in the media empire he still owns is unlikely to silence objections. The case of Il Giornale, whose editor, Indro Montanelli, left rather than bow to Mr Berlusconi's demands that it fight for his cause, provides an ominous precedent. Mr Berlusconi does not even own the paper, having handed the majority of its shares to his brother in order to keep control of his TV interests.Reuse content