The center-left opposition bloc has won the lower house in Italy's parliamentary elections by a razor-thin margin while the race for the Senate is still unclear.
Official results give the opposition 49.8 percent of the vote while Prime Minister Silvio Berlusconi's ruling conservative coalition wins 49.7 percent.
Under Italy's new election laws, the opposition will automatically control 55 percent of the seats in the lower house.
Meanwhile, officials are giving the Berlusconi coalition a one-seat margin in the senate - 155 to 154. But six seats chosen by Italians voting abroad still to be counted.
A coalition must control both the senate and the lower house in order to form a government.
Prime Minister Berlusconi and Mr. Prodi have both called for new elections if neither side controls both houses.
The election came after an angry campaign full of insults by both sides. Some information for this report was provided by AFP, AP and Reuters.