Swiss bank UBS was charged with tax fraud in Paris after being placed under investigation for allegedly helping rich French clients hide money in Switzerland, a judicial source said.

The ACP, the regulatory arm of the Bank of France, had been alerted to the undeclared accounts between 2002 and 2007.

UBS's Swiss business is suspected of illegally canvassing French customers and setting up dual accounts to hide the movement of capital into Switzerland.

A judicial source said the charges relate to money kept in accounts in Switzerland between 2004 and 2012. 

A probe was launched after a former UBS employees blew the whistle.

The bank will now have to pay a total bail of €1.1 billion euros, the source said. 

According to judicial sources, the new bail is equivalent to 42.6% of USB's after-tax profits last year and 2.8% of shareholder funds.

The move by Paris comes amid a global clampdown on tax evasion by authorities around the world. 

This week Credit Suisse said it lost €576 million in the second quarter of the year after paying a $2.6 billion fine for tax evasion to the US. 

On Monday, the OECD said countries had identified an estimated €37 billion of hidden taxes through voluntary disclosure by more than half a million taxpayers in recent years.