A key coalition partner of Italian Prime Minister Silvio Berlusconi - the centre-right Union of Christian Democrats - is leaving the government.
Silvio Berlusconi is the longest-serving premier in post-war Italy
The party said changes were needed after the coalition's crushing defeat in regional elections this month.
The Christian Democrats had four ministers in the cabinet, including the deputy prime minister, Marco Follini.
The party said before the announcement that it would continue to support the government in parliament.
But Mr Berlusconi told La Repubblica newspaper that he would not stand for the UDC leaving the government and then "blackmailing" him on every law.
Correspondents say he could now be forced to bring forward the Italian parliamentary election due next year.
On Thursday, Foreign Minister Gianfranco Fini urged Mr Berlusconi to call a vote of confidence in his government.
The prime minister said last week that he was open to the idea of calling an early general election.
The regional elections saw the opposition win 11 of the 13 regions up for re-election and around 54% of the vote.
Popular opposition to Italy's role in the war in Iraq, combined with a struggling economy, have both contributed to a decline in Mr Berlusconi's popularity.