French politician Marine Le Pen has hit back against charges of illegal party funding by European Parliament deputies from her far-right National Rally (RN) party.

Le Pen and more than 20 other senior party figures are accused of hiring assistants who worked on party affairs rather than for the European Parliament which paid them.

She told a court in Paris on Monday that parliamentary assistants paid for by the Brussels assembly were naturally involved in politics - because that was what drew them to the job in the first place.

So, she claimed, it was a false distinction to claim that they should be working solely for the parliament.

"Assistants work for their deputies, enlarging their ideas," Le Pen said.

“Just look at the number of deputies who started out as parliamentary assistants. It’s because they’re interested in politics.

"I have absolutely no feeling that I have committed the slightest irregularity, the slightest offence.”

Along with 24 other named individuals plus the party itself as a legal entity, Le Pen is accused of syphoning EU parliamentary funds to pay the salaries of party workers.

According to the prosecution case, she presided over a system for several years in which RN staff members from Paris were "taken on" as EU parliamentary assistants in Brussels.

It is being argued in court that these RN officials - who included Le Pen’s bodyguard and a graphic designer in the publicity department - rarely set foot in the EU parliament and had no role there.

On Monday, the court heard the case of Le Pen’s long-time personal assistant Catherine Griset.

Accredited in Brussels as a parliamentary aide, she was recorded as attending the assembly building for only 12 hours between August 2014 and October 2015.

But answering questions for the first time since the trial opened two weeks ago, Le Pen said it was naïve to suppose that parliamentary assistants were not taking part all the time in political work.

And she said failure to appreciate this was a sign of how the European Parliament was divorced from the reality of political life.

“The European Parliament is a bit like The Blob,” she said, referring to the 1958 film about a massive amoeba that threatens to destroy the world. “It swallows up deputies.

“In the parliament you can sleep, you can eat, you can get your hair done. Everything is contrived to keep you living in the box. Sometimes you have to say ‘Cuckoo! We’re supposed to be doing politics here!'"

A lawyer by profession, Le Pen says she will attend as much as possible of the trial - which will last till late November - despite the tense political moment in which France currently finds itself.

Her party holds a rare chance to influence events because of the permanent threat it now poses to the new government of Michel Barnier.

With the prime minister commanding the support of little more than a third of National Assembly deputies, Le Pen can bring him down at any point by backing a censure motion tabled by the left.

"We know we have the power to press the button. You know it. They know it. Everybody knows it," she said in an interview with Le Point magazine. "The government’s sell-by date is written on the box."

But Le Pen's political ambitions risk being seriously hampered by the outcome of the party funding trial.

If she is found guilty, the possible penalties include not just prison and a large fine - but also ineligibility from standing for public office for five years.

This would in theory rule out a run for the presidency in 2027 - her fourth and potentially most promising attempt.

Most likely, appeals against such a sentence could string the process out until after 2027 - and if she won the presidency she would then be immune from judicial pursuit until she left office.

Some commentators say a guilty verdict would do little in any case to harm her chances, because it would let her continue to pose as a victim of the establishment.

But others say campaigning under the shadow of a conviction would alienate many moderate voters who might otherwise choose her for the first time.