Fonseka, who lost a January 26 vote, alleged that he was robbed of victory because of rigging, electoral malpractice and undue influence on the 14 million electorate, lawyer Wijeyadasa Rajapakshe told AFP.
"We are presenting a 40-page complaint to the Supreme Court on bribery, corruption, the use of undue influence and vote rigging at the election," Rajapakshe said.
Fonseka received 40.15 percent of the popular vote compared to 57.
88 for Rajapakse at an election many had expected to be a close fight. Two weeks after his defeat, Fonseka was arrested and placed in indefinite detention.
Rajapakshe said he had earlier obtained permission from the Supreme Court for Fonseka to sign his election petition while he was being held by the military pending court martial proceedings on unspecified charges.
The country's defence secretary, Gotabhaya Rajapakse, who is the president's younger brother, has said that Fonseka was plotting a coup, a charge rejected by the ex-army chief.
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