Italy's current electoral system, approved in December 2005, uses the proportional method for attributing seats in parliament.
It is sometimes known as the 'Calderolum' after the minister (Roberto Calderoli) who was its main architect and later admitted that it was a "mess".
It has few fans - it has been nicknamed the 'Porcellum', a reference to the Latin for 'pig' - and Italy's political parties are now considering replacing or changing it in a bid to ensure election winners are able to govern effectively.
The five proposals most frequently mentioned are as follows:
GERMAN SYSTEM
This is sometimes known as a 'corrected' proportional system. On a first voting slip, voters select individual parties and parliamentary seats are distributed accordingly. Parties that get less than 5% don't get seats. On a second slip voters can choose a candidate for their constituency by name. This approach is favoured by much of the centre left and fiercely opposed by the rightwing National Alliance.
FRENCH SYSTEM
MPs are elected by name in their constituencies. If after a first round of voting no one has more than 50%, a second round is held in which all those that reached 12.5% are allowed to stand. Some parties in the centre left, including the Democratic Left, see this approach as ideal but it is firmly opposed by most of the opposition.
BRITISH SYSTEM
This is an entirely 'first-past-the-post' system. Candidates stand in their constituency where voters choose them by name. The candidate with the most votes wins. This means that it is possible for a party to win the popular vote but still end up with a minority in parliament. This system has confirmed fans in the tiny Radical party but few other supporters.
REFORMED 'PORCELLUM'
The idea, put forward by Roberto D'Alimonte of the Forza Italia party, involves altering the current system. A key change would be that the winning coalition would be given an extra packet of seats in the Senate, in the same way as happens now in the House, so as to ensure a workable majority. This is the preferred solution of former premier and Forza Italia leader Silvio Berlusconi. Other parties have said little about it so far.
'TATARELLUM'
This is named after the rightwing MP who proposed the system during the 1990s. It is used for regional elections and the National Alliance party would like to see it used nationally as well. It involves a single round of voting after which 80% of seats would be attributed proportionally and 20% according to a first-past-the-post system. The main supporter is National Alliance but four centre-left parties (Greens, Udeur, Communist Refoundation, Italian Communists) appear to see it as a possible solution.
