French newspaper Le Monde revealed on Monday "breathtaking" figures of giant global tax evasion scheme involving up to €180 billion deposited by 100,000 wealthy individuals around the world.

The paper alleges the scheme "was conducted with the knowledge, and indeed the encouragement, of the world’s second largest bank, HSBC, via its Swiss subsidiary, HSBC Private Bank."

The bank had already been placed under formal investigation in France accused of "money laundering the proceeds of tax evasion" after former banker Hervé Falciani made previous leaks to tax authorities in 2008. 

But the latest revelations from Le Monde on Monday show the scale of the bank's operation, with thousands of clients from around the world, from celebrities to arms dealers and drug taffickers all on the list.

Le Monde, which was given a USB key containing the files by an anonymous source said the revelations "will shake the international financial industry to the core".

"The holders of the accounts are striking in their variety, Le Monde writes. "French surgeons wishing to launder undeclared fees rub shoulders with… Belgian diamond traders and Al-Qaeda funders."

When it comes to the French nationals implicated in the mass tax evasion scheme, Le Monde reveals there were around 6,300 of them, whose money was split between offshore accounts in the British Virgin Islands and Panama.

Having an account in Switzerland or even offshore is entirely legal as long as it's declared to the tax man, but according to investigators only 0.2 percent of French account holders declared them.

"The use of accounts with Swiss banks by French tax residents is almost exclusively for the aim of tax evasion," said French MP Christian Eckert, in his previous report on the scandal.

One average French nationals were depositing €2 million in offshore accounts. French authorities currently have around 60 cases open against people on the list.

According to the Guardian, one of a consortium of newspapers including Le Monde which has analyzed the data since September 2014, an HSBC manager in France Nessim-el-Maleh helped hide cash from drug dealers who sold marijuana to immigrants in the Paris suburbs.

Le Monde says that French investigators have calculated that the bank had assisted over 100,000 people and 20,000 companies hide some €180 billion in 2006 and 2007.

The French government has since passed on details of clients at the bank who were evading taxes to other countries, including Argentina, Belgium, Greece, Spain, the US and the UK.

HSBC under investigation in France

In November 2014 HSBC was placed under formal investigation in France with magistrates "examining whether the bank acted appropriately between 2006-07 in relation to certain clients of the bank who had French tax reporting requirements, as well as in relation to the way the bank offered its services in the country."

In France, being placed under formal investigation is the nearest equivalent to being charged, and occurs when an examining magistrate decides there is a case to be answered.

A judicial source told AFP last year that the bank was suspected of "benefiting from the gains of tax fraud" and "laundering funds of an illicit origin by allowing thousands of clients to hide them".

The source said the bank had used numerous trusts and shell companies to help wealthy clients conceal their assets.

Many French nationals on the list have already rectified their situation with the French tax authorities, including popular comedian Gad Elmaleh. French World Cup winner Christophe Dugarry was also on the list, with Le Monde claiming he deposited €2 million in an offshore account.

In all French authorities have recovered over €300 million over the four years it has been working on the case.

HSBC has responded to the reports with an admission in a statement to the ICIJ that it is no longer operating in the way it did in 2007.

Like other private banks it “assumed that responsibility for payment of taxes rested with individual clients, rather than the institutions that banked them.”