Pfizer, the US pharmaceuticals giant which attempted to buy one of Britain's largest drug makers AstraZeneca, operated 128 subsidiaries in tax havens last year, booking $69bn in profits offshore.
That profit would have funded 60% of the world's largest pharmaceutical company's doomed $116bn (£69bn, €85bn) bid for AstraZeneca.
Pfizer had its advances rejected amid fears that it would damage the UK's scientific research sector and that it was attempting to take advantage of a lower rate of corporation tax by having a large presence in Britain.
"[If the deal does go through] we see lower tax rates [for the company] and a flexible use of financial aspects," said Pfizer boss Ian Read at a meeting with the Department of Business, Innovation and Skills in May.
However the company has repeatedly denied that its pursuit of AstraZeneca was motivated by potential tax savings.
A new report by the US PIRG Education Fund and Citizens for Tax Justice, two research and lobby groups, found that Pfizer ranked third of all the Fortune 500 companies when it comes to booking profits in offshore havens.
The study found that "at least 362 companies, making up 72% of the Fortune 500, operate subsidiaries in tax haven jurisdictions as of 2013".
Apple booked $111.3bn in offshore profits last year (all of it in Ireland) – more than any other company. If it had registered these profits in the US, its tax bill would have hit $36.4bn.
The top 30 users of tax havens collectively booked $1.2tn in offshore profits last year "for tax purposes".
That's 8% of total US GDP, and nominally, about the same size as the annual Mexican economy.
The report found that just 55 of the Fortune 500 companies disclose what they would be required to pay in US taxes had they booked the profit domestically. Collectively, they would owe $147.5bn in federal taxes.
"To put this enormous sum in context, it represents more than the entire state budgets of California, Virginia and Indiana combined," wrote the authors.
Other companies to have featured highly in the list include American Express, whose US tax bill would have reached $3bn, Nike, which would have owed $2.2bn and Bank of America ($4.3bn).
The report explained that while the profits may be officially booked offshore, they actually remain onshore invested in US assets.
"Many of the profits kept 'offshore' are actually housed in US banks or invested in American assets, but registered in the name of foreign subsidiaries," it said.
It amounts to US companies taking advantage of the relative stability of the US financial system without paying taxes for the service.
The report recommended "strong action to prevent corporations using offshore tax havens", saying that it will "restore fairness to the tax system.
The recommendations include outlawing the practice of deferring paying tax on profits, thus forcing US companies to pay tax before they have a chance to transfer profits to their offshore subsidiaries; stopping companies from licensing intellectual property to shell companies in tax havens and treating the foreign subsidiaries of US corporations as domestic corporations for income tax purposes.
Despite the strong rhetoric coming from western governments in recent months, the corporate sector's penchant for tax havens shows no sign of subsiding.
Last month, Citizens for Tax Justice reported that US companies had booked profits in Bermuda equating to 1643% of the British outposts total GDP.
Matt Gardner, executive director of the Institute on Taxation and Policy in Washington DC, told IBTimes UK: "It's a clear indicator that there's a fundamental mismatch between the amount of profits being reported in the country and the amount of economic activity in a country. It's not a smoking gun but it raises a signal that there are potentially some games being played in these countries."