Jean-Marie Le Pen, the elderly founder and former chief of France's far-right Front National, hid 2.2 million euros ($2.4 million) in a secret account in Switzerland, news website Mediapart reported Monday.

The claims come amid a bitter feud between Le Pen and his daughter Marine, who now leads the party, which has been facing a string of investigations into campaign funding both by French and European authorities.

Le Pen "kept a hidden account at HSBC, as well as the (private Swiss) CBH bank through a trust placed under the legal responsibility of his butler, Gerald Gerin," the investigative website said.

"Of the 2.2 million euros placed in the trust account, 1.7 million were kept as gold bars and coins," it added.

"Prosecutors in Nanterre (west of Paris) received this information from the anti-money laundering unit Tracfin," Mediapart said.

Contacted by AFP, neither CBH nor HSBC would comment on the report. Le Pen also refused to comment, while FN Vice President Florian Philippot told French TV channel iTELE he knew nothing about the claim.

"I don't know whether it's true, but knowing Jean-Marie Le Pen, I would find it strange if it were," Philippot said.

"I've spoken to Marine Le Pen on the phone. She is very surprised and doesn't know anything about it either. Like the rest of us, she is waiting for Jean-Marie Le Pen to clarify and explain," he added.

In 2013, the former paratrooper admitted he kept an account in Switzerland at UBS that he had opened in 1981.

The longtime FN leader and current European parliament member has been under investigation since late 2013 over undeclared assets estimated at 1.1 million euros.

A separate probe also underway focuses on the FN's campaign financing since Marine Le Pen's takeover -- with five people and the events company Riwal already charged -- while the party has also been referred to the EU's anti-corruption agency.

- 'Russian money' -

The party has also denied taking money from Russian leader Vladimir Putin in return for support for the Kremlin strongman, but recently received a nine-million-euro loan ($9.8 million) from the Czech Russian Bank.

The elder Le Pen recently repeated his claim that Nazi gas chambers were merely a "detail of history", comments that have seen him convicted in the past for denying the Holocaust.

Marine Le Pen distanced himself her father after his latest outbursts, saying he had committed "political suicide".

Under pressure from his daughter, the elder Le Pen then gave up his bid to run in a regional vote, though he had vowed not to go quietly.

He was replaced by his 25-year-old granddaughter, Marion Marechal Le Pen.

The anti-immigration NF, which under Marine Le Pen is trying to clean up its racist image, wants France to withdraw from the European Union, pull out of the euro and reintroduce the franc.

It has made a series of major gains in recent elections, topping the poll in the European election in May 2014.