Among the masterpieces listed in the trusts are a Gustave Courbet, Biche Forcée, Effet de Neige, valued at €8.2 million, along with two works by Pierre Bonnard, The fruit basket, oranges and persimmon, and Boulevard de Clichy, by night, each valued at €2.3 million. A Picasso, Mme Georges Wildenstein, is valued at €1.6 million.

The court sought to put a price tag on masterpieces spread between the United States, Switzerland and Singapour, which it said amounted to $875 million (£716 million).

Throughout the trial, Mr Wildenstein insisted that he knew little about the financial structures his brother and father had put in place. He has also argued that there was no legal obligation to report trust-held assets on his father's death.

The judge said he found it "astonishing" that France had only tightened its laws on trusts in 2011 despite a century of debate over their abuse. He also criticised investigators for not going further to prove that the Wildensteins continued to personally benefit from these offshore trusts.

Mr Wildenstein's lawyer, Hervé Temime, said his client was "very relieved".

"The error was to take this to criminal court. People are too keen to please public opinion but there are some judges who respect the law," he said, adding that he feared a backlash over claims there is a "justice for the rich".