Coming almost a decade after initial investigations started, the trial presents Le Pen with an opportunity to clear herself of accusations she has always denied as she keeps polishing the party's image in a bid to make it fit for government.

However, it also carries the risk of casting the spotlight on the RN's recurring troubles with the law.

Party officials and employees, former lawmakers and parliamentary assistants are accused of using money destined for EU parliamentary work to pay staff who were working for the RN, which at the time was called the National Front.

EU lawmakers are allocated funds to cover expenses, including their assistants, but are not meant to use them to cross-fund party activities.

Many European political parties - especially smaller ones eligible for less national funding - have used EU money to hire promising talent as aides to EU lawmakers.

Current RN party head Jordan Bardella, who is also a member of the European Parliament, used to work in such an assistant role. He is not part of the trial.

Le Pen's party, which sits with the main group of euro-sceptic and nationalist parties in the European Parliament and argues for 'France first' policies on issues ranging from immigration, energy markets and agriculture, denies the charges.

Marine Le Pen is facing charges both for her role as party leader and as an EU lawmaker who hired allegedly fictitious assistants herself.

Prosecutors say another of the defendants, Thierry Legier, had really worked as a bodyguard to Le Pen and her father Jean-Marie Le Pen, founder of the National Front, while receiving a salary as a parliamentary assistant between 2005 and 2012.

RN lawmaker and party spokesman Laurent Jacobelli told Reuters last week that Marine Le Pen was not worried about the trial.

"She knows that what we are accused of is having a different understanding, as a French party, of what an assistant role is, compared with the European Parliament's understanding," he said.

If found guilty, Le Pen and other defendants could face a potential jail sentence of up to 10 years, a one million euro ($1.12 million) fine, and be barred for up to five years from public office.

Le Pen has lost twice to Emmanuel Macron in the second round of France’s presidential elections, in 2017 and 2022, and is widely seen as a frontrunner in the next one in 2027.

The Paris public prosecutor's office opened a probe in 2016, prompted by a 2015 report from the European Parliament president to the French justice minister, followed by a police investigation.

Investigators looked at the situation of 49 RN parliamentary assistants over the past three European Parliament terms. They charged 11 RN members of the EU assembly, including Marine Le Pen and her father, for misappropriation of EU funds, and charged 13 parliamentary assistants with receiving the funds.

Jean-Marie Le Pen, 96, will not attend the trial for health reasons.

The trial will last until November 27.

The RN is under another preliminary investigation, launched in July by the Paris prosecutor's office, into alleged illegal financing of its 2022 presidential campaign.