Rome, November 9 - Secretary of the centre-left Democratic Party (PD) Pier Luigi Bersani on Friday vowed to clean up politics if he became premier at next year's elections. ''If I become president of the council of ministers I will brandish a broad sheet of morality,'' he said in a radio interview. Bersani is running against upstart Florence mayor Matteo Renzi and Puglia governor and leader of the left-wing party SEL Nichi Vendola in primaries to choose the centre-left candidate for the premiership at the end of this month. The PD secretary and veteran politician also reiterated his call for electoral reform to ensure a clear outcome from elections. ''There needs to be a premium for the winning party, also because if the premium for the winning coalition is set at 42% the bar is too high and there is a risk of ungovernability,'' he said. ''Without such a premium we risk giving birth to spurious majorities that are then unable to govern,'' he continued, adding that in the absence of a clear outcome Italians would have to return to the ballot box. Earlier this week the PD, which currently leads the polls, refused to support an electoral reform bill currently before parliament on the grounds that a new provision for a pro forma majority for the winning coalition would actually lead to greater instability since the bar would be set too high for anyone to qualify for the extra boost. Under the rule, if the votes in favor of the leading alliance reach 42.5%, an additional 12.5% would be granted to achieve a 55% majority. This is much higher than the figure originally touted. The PD is currently polling at around 27% and with centrist and left-wing allies it could get about 10-12% more, still leaving it short of the mark. Italy's President Giorgio Napolitano has made repeated appeals to politicians to agree on new rules by the elections, due to take place no later than April. However after nearly a year of stalled talks and differences at the party level, skepticism has grown that decisive reforms can be implemented in time for the vote. The current law - passed under a previous Berlusconi government and often referred to as the Porcellum, or 'Pig's dinner' - has been widely criticised for distancing politicians from voters, who effectively cannot pick their representatives, as party leaders have the power to name candidates on so-called 'blocked lists', which are then voted on.