By Frances Kennedy BBC correspondent, Rome

Berlusconi has often found himself at odds with Bossi

Thousands of supporters at a special assembly in Milan endorsed the proposal by their leader, Umberto Bossi.

However, Mr Bossi warned there was no point in staying if devolution reforms were not passed by the year's end.

Ordinary Italians say this infighting is distracting the government's attention from pressing issues, such as the cost of living and unemployment.

Ultimatum

In a crowded conference centre in Milan, Umberto Bossi laid down what appears to be an ultimatum to his allies in the centre-right coalition.

December will be a decisive month.

If the reform package is not voted, Mr Bossi said, we will know that there will be no federalism in this legislature and will want it to end swiftly.

The proposed reforms give increased autonomy and legislative powers to the regions and health, education and local policing and set up a chamber of the regions to replace the Upper House, the Senate.

As these involve constitutional changes, a series of separate votes in both houses are required and the entire process will take many months.

Mr Bossi called on his supporters to mobilise with mass demonstrations in the meantime to keep the heat on over the federalism law.

The other junior coalition partners, the post-Fascist National Alliance and the small Catholic party, the UDC, are furious at what they see as preferred status given to Mr Bossi by Prime Minister Silvio Berlusconi and his Forza Italia Party.