It won only two of the 13 regions contested in elections that ended on Monday, ceding six that it won in 2000 to the former European Commission president’s Union alliance.

Signor Prodi, who looks increasingly likely to become Italy’s next prime minister, said: “With this vote Italians are asking us to prepare to govern, to take the country forward. Berlusconi’s centre-right no longer has the support of this country’s citizens.”

With the economy struggling and the Iraq war still unpopular, voters rounded on Signor Berlusconi, postwar Italy’s longest-serving prime minister, and the results were prominently reported in the country’s newspapers despite blanket coverage of the Pope’s death.

La Repubblica, a left-leaning newspaper, said: “It’s more than a defeat. It’s a collapse.”

Il Corriere della Sera said: “It’s clear that the defeat — so burning that it can’t be played down, circumscribed or diminished — opens a political crisis within the majority. If things continue like this, the alliance is in trouble. Today in the regional vote, tomorrow in the general elections.”

The centre-right coalition retained control in only two of its traditional strongholds, Lombardy, which includes Milan, and in the prosperous northeastern Veneto region, which includes Venice. It lost key regions, including Lazio, around Rome, and Piedmont, which includes Turin.

Signor Prodi, who went to Brussels after losing the leadership to Signor Berlusconi in 2001, looks certain to be the opposition’s candidate for prime minister in a general election likely to be held May 2006.

Signor Berlusconi was reported to be furious, blaming the defeat partly on allies who allegedly prevented him from forging a wider electoral alliance.

Last night Signor Berlusconi made an impromptu appearance on a television talk show and admitted that his party had suffered a heavy defeat.

“I believe the main reason was the wave of malaise, fear and worry which is still present across Europe after the international events of September 11 and the economic slump,” he said.

Signor Berlusconi’s own Forza Italia party was the biggest loser in the coalition. Its share of the vote fell from 25.6 per cent in the 2000 regional elections to 18.4 per cent.

The right-wing National Alliance and the centrist UDC also lost ground. The formerly separatist Northern League gained slightly.

Signor Prodi’s Union took 52.9 per cent of the vote, compared with the centre-right’s 45.1 per cent.

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