rome • More than 800,000 Italians have signed a petition demanding changes to the electoral system, hoping to move Italy away from decades of political instability.

Two vans delivered the petition to a court for verification yesterday. The petition has far more than the half-million signatures needed under Italian law to force a referendum.

"Parliament, with the referendum a loaded pistol at its head, has a few months to fulfil the will of the people," said Infrastructure Minister Antonio Di Pietro.

They will put pressure on politicians to produce a new electoral law which reinforces a two-party system and reduces the power of smaller parties.

The present system was brought in under former centre-right Prime Minister Silvio Berlusconi to favour broad coalitions rather than strong single parties. The change left Prime Minister Romano Prodi with a tiny majority after his slim election win last year.

Prodi had to resign briefly in February after far-left parties in his coalition deserted him in a vote on foreign policy. He said then it was a priority to change the voting system, but no progress has been made.

The main effect of the referendum would be to hand a bundle of extra parliamentary seats in the lower house to the most successful party in an election. Under existing law, those seats are shared out between all the parties in the winning coalition.

Prodi also hopes to consolidate a more stable system by creating a single main centre-left party by merging the two existing big players into the Democratic Party. The party is expected to be created this year.

This might force the centre right to do the same, sweeping away the unstable multi-party system.