“(There was) so much vote-rigging, I am confident the result must change,” Mr Berlusconi told reporters in Rome.
Mr Berlusconi’s House of Freedoms bloc lost the election to Romano Prodi’s Union coalition by a tiny margin.
“The rigging was all in one direction, it was absolutely not evenly spread,” he said.
“We have to check the records of 60,000 polling stations, one by one. The result must change because there was too much fraud in several parts of Italy.”
The billionaire leader, who has refused to concede defeat to Mr Prodi and earlier denounced what he called “a great many irregularities” in Sunday and Monday’s vote. He asked the journalists: “Did you think you’d got rid of me?”
Mr Prodi brushed aside the flamboyant premier’s claim, telling him he was in the grip of an “identity crisis” and it was time to step aside after five years in power.
“Berlusconi has been trying to spread concern and in spite of his defeat he continues to cast doubt on the legality of our victory. I can assure you there is no doubt about our victory,” Mr Prodi said in his northern hometown of Bologna.
“We won and it is useless for Berlusconi to try to delay (recognition of our victory). Berlusconi must go home.”
However, at his first major news conference since his seat-of-the-pants win, he conceded the election chaos could leave Italy in political limbo without a government until mid-May.
He said he would likely have to wait until a new president takes office before he would be able to form a government.
President Carlo Azeglio Ciampi’s seven-year mandate is set to end on May 18 and the 85-year-old indicated on Wednesday that he wanted his successor to install the new government.
The first meeting of the newly-chosen parliament takes place on April 28.
Mr Prodi said that in the meantime he would forge ahead with plans for his administration, and had held talks with coalition partners on the composition of his cabinet.