James Ibori -- the former governor of oil-rich Delta State from 1999-2007 -- admitted in February in Southwark Crown Court he embezzled nearly $80 million through inflated state contracts and kickbacks and stole money from state accounts with help from employees, The Wall Street Journal reported.
Judge Anthony Pitts called the $80 million amount "ludicrously low," and estimated the amount to be in excess of $300 million, The Guardian reported.
Robert Palmer of Global Witness, an organization that campaigns against corruption, called for an investigation into British banks for their role in the money-laundering scheme.
"By doing business with Ibori and his associates, these banks facilitated his corrupt behavior and allowed him to spend diverted state assets on a luxury lifestyle, including a private jet and expensive London houses, while many Nigerians continue to live in poverty," Palmer said.
The Metropolitan Police in London said the investigation of Ibori, which began in 2005, marked the first of its kind by the department's Proceeds of Corruption Unit, established about six years ago to investigate alleged corruption by foreign officials, The Wall Street Journal said.
Dubai authorities arrested and extradited Ibori in May 2010 at the request of British police.