- guardian.co.uk, Monday September 18 2000 02.21 BST
In a move which stunned the government, the Northern League said it wanted to force the transfer of powers from the state to the wealthy region it controls.
The government called the plan dangerous, unconstitutional and liable to spin out of control.
The threat could also unravel the centre-right opposition, led by Silvio Berlusconi, which welcomed the Northern League into its coalition on the condition that it renounced separatism.
A poll in yesterday's La Repubblica showed a coalition led by Mr Berlusconi, a former prime minister, and including the Northern League would defeat the centre-left government in the national elections which are due in the spring.
Tentative government plans for fiscal devolution have come to nothing, allowing the League's leader, Umberto Bossi, to seize the initiative.
Politicians in the relatively impoverished southern regions have begun forming alliances as the prospect of isolation looms.
Lombardy, which will hold the referendum for control of the police, health, trade and education on the same day as the general election, is expected to be followed by Venetia and Piedmont, which have resented the south's drain on resources virtually since Italy was unified in 1861.
"There is unlikely to be blood on the streets - whatever the response, the vote can have no immediate legal effect," a political scientist at the American University of Rome, James Walston, said.
"But if the three biggest and richest regions of the north vote in favour of devolution, the political effect will be devastating.
"Bossi has tossed a verbal hand grenade into political discourse. This initiative could take on a momentum of its own."
Mr Bossi's inconsistency about the level of autonomy he wants has rattled Italy since his party emerged in the early 1990s.
Leaders of the government coalition condemned his ultimatum as an attack on the unity of the state.
"Regional referendums are objectionable from a legal point of view; they are outside the law," the prime minister, Giuliano Amato, said.
By challenging Rome's legitimacy the referendums could unleash a crisis in Italy's democratic institutions, he said.
But some in the government sensed a chance to attack the resurgent opposition, which seeks to contrast its discipline with the fractious centre-left.
"It is demagoguery which will boomerang on them," said Massimo Cacciari, who survived the left's hammering in Venezia in last April's regional election.
The opposition hoped it had tamed the League's mercurial leader, but yesterday he led supporters in a ritual of carrying water from the Po river to the Venetian lagoon, a tradition he invented three years ago to rally support for his notional independent state "Padania".
Mr Bossi insisted that he no longer wanted independence, but his coalition partners feared that he was already slipping the leash. His walkout caused the collapse of Mr Berlusconi's first government after seven months in 1994.
In a relationship patched up this year, Mr Berlusconi promised to dole out limited autonomy in return for the League's votes, which he is thought to need to return to power.
Yesterday his Forza Italia party said it backed the referendum call, but analysts said the opposition's unity was in danger of fracturing.
