Tax-haven abuse by multinationals is exacerbating the global wealth gap and putting an excessive burden on developing countries, according to a damning new report from the nonprofit Oxfam.

Coming just a week after the release of what have come to be known as the Panama Papers, the report sheds further light on the untiring efforts by companies and wealthy individuals to avoid paying taxes using offshore havens and loopholes in tax laws, starving national governments of investment funds for education, health care and infrastructure.

“ ‘So many companies pride themselves on corporate social responsibility, but we want that to be redefined to put tax and tax responsibility upfront.’ ” — Raymond Offenheiser, Oxfam America

See: Declining corporate profits weighing on U.S. tax revenue

“We have been raising the alarm about dramatically increasing inequality around the world, that threatens to undermine the progress made in fighting global poverty,” Raymond Offenheiser, president of Oxfam America, told reporters on a conference call. “The global tax system is fundamentally broken, and it’s having the harshest impact on poor people.”

Read: Britain, Ireland, Switzerland will be big winners from Panama Papers

The numbers are certainly grim. The wealthiest 1% now have more wealth than the rest of the world combined, the report found. Just 62 individuals account for as much same wealth as 3.6 billion people, or half of humanity, compared with the 388 individuals required to clear that barrier as recently as 2010.

The lobbying machine

Oxfam analyzed data from the 50 biggest U.S. companies based on tax returns and other public documents for the six-year period from 2008 to 2014. The agency then compiled the data into categories, including profits as reported, taxes paid, federal support, money held offshore and money spent on lobbying.

Read:Why don’t the bad guys simply hide their money in gold?

The data showed the companies in the study earned $4 trillion in profits in the period and paid $1 trillion in taxes globally, $412 billion of which was directed to the U.S. That gave them an effective tax rate of just 26.5%, as compared with the U.S. corporate tax rate of 35% and the 27.7% rate paid — on average, by Oxfam’s calculation — in other developed countries.

Read: America’s super-rich are hiding trillions of dollars in plain sight

At the same time, those companies spent $2.6 billion on lobbying and received nearly $11.2 trillion in federal support in the shape of loans, loan guarantees or bailouts. They used a network of more than 1,600 disclosed tax-haven subsidiaries to place about $1.4 trillion of cash offshore (and may have many more such companies that they are not obliged to disclose).

Oxfam acknowledged that the period under review includes the financial crisis of 2008-09 and the emergency measures that were created to deal with it. Most of the bailout loans have since been repaid with interest, and not all sectors or companies were beneficiaries.

“Nonetheless, the data is useful to observe in aggregate because it puts in stark relief the taxpayer-financed benefits large companies in general enjoy in relation to the taxes they pay,” said the report.

“The $11.2 trillion number is eye-popping,” said Julie Beals, Oxfam director of private-sector engagement, on the call. “Our view is that something is profoundly wrong with that.”

Hoarding cash

The company with the most money offshore was Apple Inc. AAPL, -3.17% , at $181 billion, followed by General Electric Co. GE, -2.41% , at $119 billion, and Microsoft Corp. MSFT, -1.24% , at $108.3 billion, the data showed.

The company with the most subsidiaries based in tax havens was Morgan Stanley MS, -0.33% , with at 210 such entities, followed by Pfizer Inc.’s PFE, -0.51% 151 and PepsiCo’s PEP, -1.29% 132. Morgan Stanley also had one of the lower effective tax rates at just 7.9%.

GE spent the most on lobbying at $161 billion, followed by oil giant Exxon Mobil XOM, -1.61% , at $121 billion and Boeing Co BA, -3.81% , at $117 billion.

Exxon had the greatest profit, at $432 billion, but it also had the third-highest effective tax rate: 41.1%. ConocoPhillips COP, -0.61% had the highest tax rate, at 65.8%, followed by Chevron Corp. CVX, -0.73% , at 41.9%.

Companies as corporate citizens

Oxfam is now calling on Congress to lead an overhaul of international corporate tax rules and cautioned against a “race to the bottom” in corporate taxation levels. “Too often the debate is about lowering corporate tax rates, but the question is how low to compete with a tax haven with a rate of zero?” said Offenheiser. “That is an absurd proposition.”

Read: Businesses should pay their fair share after tax reform

As a first step, the agency is calling on Congress to pass the “Stop Tax Haven Abuse Act,” which includes a number of measures that would help rein in abuse, including a mandatory country-by-country-reporting (or CBCR) requiring companies to disclose where they do business and where they pay taxes. That measure has already been adopted in the European Union for banks and is expected to be extended to cover 10% to 15% of multinationals operating there this summer.

Read:EU launches push to thwart corporate tax avoidance

But companies, too, must commit to paying their fair shares, much in the way they unveil environmental or sustainability goals to show they are good corporate citizens. “So many companies pride themselves on corporate social responsibility, but we want that to be redefined to put tax and tax responsibility upfront,” said Offenheiser.

The Panama Papers leak may help provide an incentive, as it will keep the tax story in the news, he said. The tenor of the current U.S. presidential election campaign may be another support, as the public demonstrates concerns about whether the political system and the economic system is rigged in favor of the wealthy.

“We hope all this will help push the conversation forward,” Offenheiser said.

Read on:Dodging tax is not just about offshore havens