The graft trial of France's former rightwing president Nicolas Sarkozy and 12 others has begun in Paris, with Sarkozy facing a potential 10 years in prison if convicted on all charges.

The trial, the culmination of a 10-year anti-corruption probe, also involves Claude Gueant, Sarkozy's former secretary-general and interior minister, Brice Hortefeux, another former interior minister, and Eric Woerth, a budget minister under Sarkozy who is now a lawmaker in Emmanuel Macron's centrist party.

All deny any wrongdoing.

The trial, which could last four months, has been called the biggest political financing scandal in modern French history and includes allegations the former president accepted 50 million euros ($51.8 million) in illegal election campaign contributions from former Libyan leader Muammar Gaddafi.

Investigative magistrates plan to prove a "corruption pact" between Sarkozy and Gaddafi that began in 2005 and involved intermediaries delivering suitcases full of money for Sarkozy's successful 2007 presidential campaign.

The court will be told the money afforded the Libyan government diplomatic, legal, and business advantages throughout the early stages of Sarkozy's presidency, which ran from 2007 to 2012.

But Sarkozy was a strong supporter of NATO airstrikes that rocked the Libyan regime in 2011 and helped end Gaddafi's time in power, culminating in his death at the hands of rebels in October 2011.

Gaddafi's son, Saif al-Islam Gaddafi, seemed to support the prosecutors' claims in March 2011 when he told Euronews: "Sarkozy has to give back the money he accepted from Libya to finance his electoral campaign. We financed his campaign and we have the proof … The first thing we're demanding is that this clown gives back the money to the Libyan people."

Sarkozy has said the allegations are part of a conspiracy against him, fueled by a desire for revenge among Gaddafi's supporters.

The Agence France-Presse news agency quoted his lawyer, Christophe Ingrain, as saying Sarkozy "is awaiting these four months of hearings with determination".

"He will fight the artificial construction dreamed up by the prosecution," Ingrain said. "There was no Libyan financing of the campaign."
Gueant's lawyer, Philippe Bouchez El Ghozi, said the charges amount to no more than "assertions, hypotheses, and other approximations".

Sarkozy has already had several brushes with the law and was convicted of corruption and influence peddling last month in a trial related to his attempts to secure favors from a judge. He was ordered to wear an electronic tag for a year after that conviction, which he plans to challenge in the European Court of Human Rights.

And he was convicted recently of attempting to hide illegal overspending in the 2012 presidential election campaign, which he also plans to appeal.

Additionally, he is being investigated over allegations that could lead to two more trials.