Italian Prime Minister Silvio Berlusconi is due to address both houses of parliament today to try to save his fragile government.
Silvio Berlusconi has survived previous votes of confidence
Mr Berlusconi could lose the support of the National Alliance (AN), a key coalition partner, after reversing a decision to form a new government.
Instead Mr Berlusconi has called a vote of confidence in his administration.
If he loses the government must resign and a general election may be called a year ahead of schedule.
Mr Berlusconi's decision to hold the vote took allies and foes by surprise.
He had been expected to resign on Monday, enabling him to make a major government reshuffle and announce major policy changes.
But instead he told the president he would put his authority to the test in a parliamentary vote.
The AN is the second largest party in the coalition, and its departure would bring down the government.
It believes current policies are skewed in favour of the country's more prosperous north, represented in the coalition by the Northern League.
BERLUSCONI IN CRISIS
4 April: PM's party wins just two of 13 regional elections
14 April: National Alliance calls for vote of confidence
15 April: Union Of Christian Democrats pulls out of governing coalition
18 April: PM hints that he may resign and form new government
19 April: Vote of confidence announced
Mr Fini said: "The National Alliance does not agree with the decision the prime minister took yesterday... Berlusconi has reinforced the already widespread negative impression that the League is the boss of the coalition."
But he said he would continuing supporting Mr Berlusconi in parliament.
The smallest of the four parties in the coalition, the Union of Christian Democrats, left last week after a heavy defeat for the prime minister in regional elections.
Forza Italia, Mr Berlusconi's party, indicated on Sunday that if the UDC refused to rejoin the coalition it would call an early general election.
On Monday ministers suggested that Mr Berlusconi had accepted the demands and would resign in order to form a new government and avoid elections.
But the prime minister emerged from a meeting with President Carlo Azeglio Ciampi, at which he was expected to tender his resignation, denying he had done so.
The centre-left opposition described Mr Berlusconi's actions as an "indecent farce".
Popular opposition to Italy's role in the war in Iraq and a struggling economy have contributed to a decline in Mr Berlusconi's popularity.
The regional elections saw the opposition win 11 of the 13 regions up for re-election and around 54% of the vote.