BUENOS AIRES, Argentina (AP) -- Argentine prosecutors put a former president on trial for bribery on Tuesday, accusing Fernando de la Rua of bribing senators for votes.

A three-judge panel already has ruled that $5 million was paid to a group of senators in exchange for their votes to remove worker protections in the year 2000, when the International Monetary Fund was making workforce flexibility a requirement for extending loans to Argentina. The law, which enabled companies to fire workers without cause or severance pay, was overturned in 2004.

Now prosecutors must prove the payments were ordered by De la Rua, who served from 1999 to December 2001, when the IMF refused to extend more loans and the economy collapsed. Deadly riots followed, forcing de la Rua to flee by helicopter from the rooftop of the presidential palace.

De la Rua's co-defendants include his liaison to Congress, former parliament secretary Mario Pontaquarto, who confessed a decade ago to delivering the money on the orders of De la Rua himself.

Pontaquarto said he picked up the $5 million from Argentina's Intelligence Service, giving $4 million to one senator, Emilio Cantarero, and $1 million to another, Jose Genoud. Cantarero now suffers from Alzheimer's disease and Genoud committed suicide, but Pontaquarto said he helped prosecutors compile solid evidence.

"I'm looking for the truth to put an end to all of this," Pontaquarto said as he entered the courtroom Tuesday, adding that he's not afraid to go to prison.

"If there's no conviction for me, who turned myself in, no one will be convicted and impunity will result," he said. "Society has condemned this, and what I want is for the justice system to condemn it as well. I'm not interested in De la Rua's lies. This was the most serious act of institutional corruption since the return of democracy" in 1983, after seven years of dictatorship.

De la Rua's defenders handed out pamphlets at the courthouse Tuesday noting that Pontaquarto had been convicted of embezzling government travel money and saying he should not be believed.

"This is an absurd case, full of contradictions, built on rumors that lack any evidence," De la Rua declares in the pamphlet. "Pontaquarto has accused me without proof, with a discourse based on contradictions that were never proven. What credibility could this person have? None."

The trial is expected to stretch well into 2013 with nearly 340 witnesses lined up including President Cristina Fernandez, who was granted the right to submit written testimony. Fernandez was an opposition senator at the time of the crime and is not accused of taking a bribe.

Also charged with bribery are former intelligence chief Fernando de Santibanes and former Labor Minister Alberto Flamarique. Four former senators are charged with accepting the bribes: Alberto Tell, Augusto Alasino, Remo Costanzo and Ricardo Branda.

Junta leaders have been tried for human rights violations in recent years, but De la Rua is only the second democratically elected former Argentine president to face trial. The other was his predecessor Carlos Menem, who was acquitted in November of arms trafficking in the early 1990s.