Financial data lacking from biggest companies: Watchdog

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If you're looking for financial information about many of the world's biggest corporations, you'll have a hard time finding it, according to a new report by a watchdog group.

The job gets even tougher when you're looking for financial information about companies in China or U.S. tech giants, like Amazon or Google, according to Transparency International's latest report.

"Surprisingly, the sector that makes greater transparency possible is one of the least transparent," the group said. Amazon, Apple, Google and IBM all scored less than three out of 10, the organization said.

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An IBM spokesman told Reuters the company publishes a full list of every subsidiary and country-level business in its annual report. Amazon, Apple, and Google did not immediately respond to emails from CNBC for comment.

The report named Bank of China, Honda Motor, Shanghai-based Bank of Communications, Agricultural Bank of China and Russia's Sberbank as the five least transparent companies. Preliminary findings were provided to individual companies, who were invited to comment or suggest corrections. Of the 124 companies reviewed in the report, 84 provide such feedback, it said.

To see how the companies responded in the report, click here.

The Berlin-based anti-corruption watchdog rated companies based on three criteria. First it looked at a company's anti-corruption programs, including policies on gifts and employee training.

Next, it looked at how transparent companies are in disclosing the finances of subsidiaries and affiliated operations.

"Organizational transparency is important for many reasons, not least because company structures can be made deliberately opaque for the purpose of hiding the proceeds of corruption," the group said in its report.

Lastly, it looked at country-level detail of companies with operations around the globe.

The group said that roughly three-quarters of the 124 companies reviewed, for example, do not disclose the taxes they pay in foreign countries, and nearly half publish no information on revenues abroad.

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European companies were among the most transparent, based on the group's criteria. Italy's Eni, Britain's Vodafone and Norway's Statoil were ranked among the highest.

The group said its findings were based on information available on company websites along with public documents including annual reports and stock exchange filings.