Signor Prodi, who won April’s election with a slim majority, faces growing unrest over his 2007 budget from employers and trades unions, and also from within his nine-party coalition.

He raised the stakes yesterday by announcing that a motion on controversial tax reforms tomorrow would be a vote of confidence in his Government.

But his troubles were highlighted yesterday when the Government lost a vote in the Senate because a number of centre-left senators failed to turn up. Two former prime ministers are already being touted as stop-gap successors.

Silvio Berlusconi, the opposition leader and former Prime Minister, said the crisis summit, to be held at a state-owned Renaissance villa in Rome, showed that the Prodi Government was “falling to pieces” after only six months. He recalled that last time Signor Prodi — his eternal rival — won power in 1996, he lasted two and a half years as Prime Minister before losing a confidence vote when the hard Left withdrew support.

“This time it won’t be two and a half years but a great deal less,” Signor Berlusconi predicted. Gianfranco Fini, leader of the Far Right Alleanza Nazionale and Foreign Minister in the previous Berlusconi Government, said that “if the Prodi Government falls there will be new elections”. Some members of the centre left, however, noted that when Signor Prodi resigned in October 1998 the coalition remained in power under Massimo D’Alema, a leader of the ex-Communist Democrats of the Left and now Foreign Minister. He in turn was succeeded by Giuliano Amato, the present Minister of the Interior. Both are again being mooted as possible successors.

Enrico Boselli, head of the small Italian Socialist Party (SDI), said that there was “a behind-the-scenes campaign against Prodi with the aim of bringing him down . . . It is one thing to criticise errors in the budget, another to make out the Government is incapable of putting the economy right”.

Roberto Villetti, Signor Boselli’s deputy, said there was “a passive plot against Prodi — he is hanging by a thread but no one is doing anything to save him”. However, Vannino Chiti, the Minister for Relations with Parliament, said that the Prodi Government would last a full term.

Fabio Mussi, Minister for Universities, said that the Government had inherited a dire economic situation from Signor Berlusconi, and devising a solution was “like navigating a dangerous reef. We are having problems communicating with the country, but we are on the right course”. Emma Bonino, the Minister for Europe, said: “If people are plotting a Plan B in secret rooms then they are wasting their energies and damaging the country.”

Signor Prodi is said to have assured the dissenters that the tough budget is “Phase One” of an emergency plan to reduce Italy’s huge deficit through spending cuts but also through lower taxes for the poor and higher taxes for the better-off, to be followed in due course by a more upbeat “Phase Two” to boost growth.

Signor Prodi enjoys a clear majority in the Lower House but took office with a majority of only two in the Senate, since reduced to one because of a defection. Another waverer has prompted some observers to claim that Left and Right were now level-pegging in the Senate on the budget.

This would make Signor Prodi dependent on the seven Life Senators. The draft budget aims to cut the deficit by about €15 billion (£10 billion) next year. But last week Standard & Poor’s and Fitch downgraded Italy’s credit rating because of its “inadequate response to structural economic and fiscal challenges”. Signor Prodi has already had to revise a plan to force businesses to use severance pay funds for private pensions, and restore a billion euros in planned cuts in local authority funding after protests by local mayors.

THE REVOLVING GOVERNMENTS

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