ROME (Reuters) - The Italian Chamber of Deputies on Thursday gave its final approval to a contested electoral law that is likely to penalize the anti-establishment 5-Star Movement in next year s election. The bill, which is supported by the ruling Democratic Party (PD) and mainstream center-right opposition parties, was approved in a secret ballot by 375 votes to 215, and will now move to the upper house Senate for further debate. The so-called  Rosatellum  law favors parties which group together ahead of the election. The 5-Star refuses to join any alliance and says the reform could cost it at least 50 seats in the next parliament, hobbling its chances of taking power. 