Italy's reforms minister and leader of the populist Northern League, Umberto Bossi, has threatened to pull out of Prime Minister Silvio Berlusconi's centre-right government.
Bossi is threatening to vote against the government
The row is over public broadcasting issues, compounded by rifts with the Catholic coalition partners.
Mr Bossi wants Rai Due - one of public broadcaster Rai's three TV channels - to relocate north from Rome to Milan.
"A TV channel belonging to the North is needed, because that is where 60% of the TV licence is paid. Imagine us not having a TV channel," he told a party rally in the northern town of Ivrea.
I feel extreme discomfort among my men: It is difficult for us to support those we have being going against for so many years
Not moving the channel would be "an attack on federalism, an attack against us, there would be no longer any reason for being part of the government," he said.
The Italian TV board was forced to resign in February over its decision to move Rai Due to Milan, a move strongly opposed by some of the Northern League's coalition partners.
Mr Bossi also said the Northern League's relations with the Catholic parties were under strain.
"The grassroots are getting uncomfortable, but so are many old Christian Democrats in the ruling coalition, because it is difficult for us to agree with each other," he said.
"I feel extreme discomfort among my men: It is difficult for us to support those we have being going against for so many years," he added.
On Wednesday, the Northern League accused its Catholic coalition partners of being behind the government's surprise defeat in a key vote on media laws.
The laws sought to limit the number of TV channels any individual could own, potentially threatening Mr Berlusconi's private media interests.
The party's announcement that it intends to run independently in the first round of local elections in May is also creating strains within the coalition.
Silvio Berlusconi's government has only a very slim majority of around 12 in the Senate, Italy's upper house. The Northern League can count on the support of 17 senators.
Mr Bossi's withdrawal from the first Berlusconi government in 1994 led to its fall after only seven months.
If Mr Bossi were to carry out his threat and withdraw support, Italy could find itself once more without a government - this time on the eve of the EU presidency, which Italy will assume from 1 July.
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