Italian Prime Minister Silvio Berlusconi's former allies withdrew from the government on Monday, paving the way towards the opening of a political crisis.

The European Policies Minister Andrea Ronchi, Deputy Minister of the Economic Development Ministry Adolfo Urso and the undersecretaries of state Antonio Buonfiglio and Roberto Menia resigned from office, ANSA news agency reported.

All four belong to the newly formed Future and Freedom Party, recently launched by House Speaker and former Berlusconi ally Gianfranco Fini as a center-right alternative to the governing People of Freedom Party.

The Future and Freedom Party has thus officially withdrawn its confidence to the government but pledged to support the crucial approval of the 2010-2012 budget plan for the benefit of the country's weak economic recovery, said its members.

In case of early elections, the members of the Future and Freedom Party are considering building a coalition with the main centrist groups in a bid to "launch a government focused on implementing the vital reforms this country is badly need of," said Adolfo Urso.

The move stands as the definite blow to Berlusconi's ailing majority. The government is now openly facing a crisis and must handle two emergencies: a necessary reshuffle and the need to find another stable majority if it is to carry on with the current legislature, set to expire in 2013.

Despite rejecting the requests of his former allies to immediately step down from office, Berlusconi has decided to present a vote of non-confidence just at the House, considering the vast support he still enjoys at the Senate.

Were he to lose the vote, the premier said he would hold elections solely for the renewal of the House. However, the decision to have only one branch of parliament vote the motion of confidence and be eventually re-elected by citizens might be a constitutional breach, according to local commentators.

Italian President Giorgio Napolitano has summoned for Tuesday both Senate leader Renato Schifani and House Speaker Gianfranco Fini to discuss the parliamentary situation and ponder whether there are elements to go on with the legislature or call for an early ballot.

According to the Italian constitution, the president has the power to formally open the crisis and call for new elections if he thinks it's impossible to form a new majority and push through with the government program.

Berlusconi in the meantime has called for an extraordinary meeting of his People of Freedom Party, which has defined the former allies' withdrawal from government "a betrayal."