Rome, January 25 - Democratic Party (PD) leader Pier Luigi Bersani said he was irked Friday by outgoing Premier Mario Monti's latest jab at the PD, over troubled Siena bank Monte dei Paschi di Siena (MPS), at the centre of a row over previously undisclosed derivatives losses. "He (Monti) finds a flaw in the PD every day while I never heard any for a year,' Bersani said, referring to the PD's support for the Monti government that folded in December after ex-premier Silvio Berlusconi withdrew support. The PD has run Siena for decades and it is represented on the foundation that controls MPS, Italy's third-largest lender and the country's oldest bank. Earlier this week MPS said it had just discovered losses of 720 million euros from two derivatives deals, with Japanese bank Nomura and German bank Deutsche Bank, increasing criticism of its running after a 3.9-billion-euro government bailout last year. Monti said Friday that political involvement in banks had to be "rooted out", calling it "an ugly beast". "The PD is involved (in the MPS case), it has always had a lot of influence on the bank and on Siena's political life," Monti said. While Berlusconi did not attempt to make political capital out of the case, saying he was "grateful" to MPS because it had helped fund a major construction scheme in Milan, his key ally, Northern League leader Roberto Maroni, claimed the affair "smells of kickbacks and if that is proven the government should appoint a commissioner" to run the bank. Monti, who is polling behind Berlusconi and frontrunner Bersani for the February 24-25 elections, has taken several swipes at the PD lately, criticising it for blocking labour-market reforms and urging it to drop its alliance with the hard-left SEL party. But the outgoing premier, who pundits say may have to forge an alliance with the PD in the Senate, has been even more severe on Berlusconi, saying he could work with his People of Freedom (PdL) party but only if three-time premier Berlusconi steps down as leader.