Italians have begun voting in a referendum on landmark pension reform plans to raise the retirement age.
Mr Prodi's broad coalition suffers from internal tensions
Workers are expected to approve the proposals by Prime Minister Romano Prodi's centre-left coalition in the three-day, non-binding vote.
But a poor turnout or narrow victory could boost calls for amendments in the plans when they reach parliament.
The deal proposes to raise Italy's retirement age from 57 to 58 by next year and to 60 by 2011.
The changes would also allow for the early retirement of workers in jobs considered particularly difficult and provide for employees without full-time staff jobs.
Employers and most unions back the plans, but the two communist parties in Mr Prodi's coalition oppose them and could cause problems in the Senate, where the government only has a one-seat majority.
Critics want to renegotiate the reforms to extend the categories of workers who would be eligible for early retirement.
The plans would soften a law passed under the right-wing administration of Mr Prodi's predecessor, Silvio Berlusconi, that raised the retirement age to 60 by next year.
If the reforms are passed, Italy, which has Europe's oldest population, would still have one of the lowest retirement ages in the EU.