Fernando Poe first made his name as a film star

Mr Poe, who lost to Mrs Arroyo by more than a million votes, has accused her campaign staff of widespread electoral fraud.

He has demanded a recount of about 60% of the votes.

A spokesman for Mrs Arroyo said she welcomed Mr Poe's complaint in the interests of fair play, and she believed he had made the right decision by taking the matter to court rather than organising protest demonstrations.

'We want the truth'

In a 28-page petition to the Philippine Supreme Court, Mr Poe's lawyer Sixto Brillantes set out the former actor's complaints.

"We just want the truth to come out," Mr Brillantes told reporters.

Mr Poe has accused his rival of "massive and widespread electoral fraud, anomalies and irregularities" to win the 10 May polls.

The opposition accuses Ms Arroyo's camp of electoral fraud

His supporters claim that Ms Arroyo manufactured or switched ballots to manipulate the results of the poll.

Mr Poe's running mate, former senator Loren Legarda, filed a separate complaint questioning the victory of Ms Arroyo's vice president, Noli de Castro.

Presidential spokesman Ignacio Bunye said: "We are glad that Mr Poe and Ms Legarda chose only the legal and proper forum to contest the elections."

"We are ready to defend our case and we are confident that we stand on solid ground," he said.

"Nonetheless, we will continue to extend our hand to all our former adversaries for the sake of unity and reconciliation."

Mr Brillantes estimated that an investigation into the election results would take about three years - half Ms Arroyo's term in office.

Under the Philippine constitution, the Supreme Court has the sole authority to decide election matters, but there is no deadline and cases can drag on for years.