Ping accused the court of "bias" during a press conference following its ruling in the early hours of Saturday upholding Bongo's victory in the contested August 27 presidential election.
"I will not retreat".
Ping said he has no faith in the judicial body because of its ties to the Bongo family.
Initial vote tallies had shown Bongo winning by 6,000 votes, but after examining voting records, the court said the incumbent in fact had won by almost twice that margin - 11,700 votes.
President Bongo won August's election just by 600o votes but the opposition say the election was rigged. Ping's legal team was absent from the courtroom as the ruling was announced.
LIBREVILLE, Sept 22 Gabon oil workers will stay at home from Thursday over concerns about potential violence when a court delivers a final verdict on the central African country's disputed election result, their union said.
Ping's refusal to concede raises the specter of prolonged unrest in Gabon, the oil-rich nation where Bongo became president in 2009 after the death of his father.
In a speech immediately after the court ruling, Bongo renewed a call for an open political dialogue to bring his allies and opponents together to work together in the country's best interest. "These voices, embodying political violence never before in our country, promise a lasting instability if the result of the Court they were not favorable", acknowledged Alain-Claude bile-By-Nze.
The petition alleges irregularities in Haut-Ogooue province, where Bongo won 95 percent on a turnout of 99.9 percent.
But Gabonese ministers have vowed to maintain order, and warned Ping he could be held responsible if fresh violence breaks out.
Bongo was announced as the victor of the country's general elections, which were held late last month.
Demonstrators set fire to the parliament and clashed violently with police, who arrested around a thousand people.
Gabon's newly re-elected president, Ali Bongo, said Saturday that he would seek to form a new government based on a national political dialogue that will "most likely" include leading opposition figures.
A European Union observer mission stated it had uncovered anomalies in the province's results.