The ICIJ said it had reviewed around 28,000 pages of leaked documents which detailed complex financial structures that enabled companies to dramatically slash their tax liabilities.

The organization said hundreds of billions of dollars had been funneled through Luxembourg as part of the agreements, wiping billions of dollars in taxes from the companies’ bottom lines.

Global accounting giant PricewaterhouseCoopers had helped the companies in question secure at least 548 tax rulings in Luxembourg between 2002 and 2010 according to an ICIJ analysis of the documents.

The documents uncovered details of Advance Tax Agreements — deals which set out how companies will be taxed.

“It’s like taking your tax plan to the government and getting it blessed ahead of time,” the ICIJ quoted Connecticut School of Law tax expert Richard Pomp as saying.

“And most are blessed. Luxembourg has a very user-friendly tax department.”

The ICIJ said its investigation had involved a team of more than 80 journalists from 26 countries working for outlets including The Guardian, Le Monde and Germany’s Suddeutsche Zeitung.

– ‘Magical fairyland’ –

The Guardian said in its report of the investigation that the arrangements forged between the companies and the tiny EU member state were “perfectly legal.”

But it said the agreements were enabling tax avoidance on “an industrial scale.”

Other companies that benefited from the schemes included Burberry, Procter & Gamble, Heinz, JP Morgan and FedEx.

The ICIJ said some companies had been able to achieve effective tax rates of less than one percent on profits channeled through Luxembourg.

It said many cases involved Luxembourg subsidiaries of the companies in question, even if they maintained only a marginal business presence in the country. It said 1,600 companies were registered at one address alone.

The Guardian quoted US Treasury tax expert Stephen Shay as saying Luxembourg was akin to a “magical fairyland.”