Lawmakers are under pressure to meet the premier’s summer deadline for reform, part of Renzi’s broader revamp of the Italian political system.
A total of around 3,000 amendments have been put forward to the law, which was discussed on Tuesday
The government is said to be leaning towards the model in France, where senators are elected by officials across the country rather than by public vote
But the proposal is facing opposition from part of Renzi’s own Democratic Party (PD), with Senator Vannino Chiti presenting his own model of elected representatives.
The move has also faced opposition by Silvio Berlusconi’s Forza Italia.
Constitutional reforms are badly needed in Italy not only to re-shape the Senate but also to change the functions and powers of the upper and the lower house. This might actually help make the whole system work faster
Renzi has made Senate reform one of the hallmarks of his premiership, aiming to cut the number of representatives from the current 320 and instead have mayors and regional presidents as senators. Under the proposed overall, Senate powers are also due to be reduced.