More than one in five of Britain's largest corporations are channelling political donations to favoured candidates ahead of next month's elections in the US, according to leading politicians, judges and pro-transparency watchdogs.
As election year reaches its climax, America is forecast to experience the most extensively corporate-influenced race for the White House, and for control of Capitol Hill, in living memory.
Among the industries already well versed in bankrolling US politics are finance, pharmaceuticals, energy and defence. British multinationals such as HSBC, Barclays, Experian, Prudential, GlaxoSmithKline, AstraZeneca, BP, Shell and BAE all have political action committees (PACs) that channel donations from employees to US politicians.
Some 14 of the top 50 most active foreign-controlled PACs have parent groups listed in London, according to the US-based Centre for Responsive Politics.
This makes the UK the biggest hub for foreign multinationals seeking to exert influence at the US ballot box on 6 November. Despite this, some FTSE 100 groups continue to tell shareholders in annual reports and elsewhere that they do not make political donations.
Companies are able to make such claims because PACs receive their funds from US employees - often led by the most senior American executives - and only dip into company coffers to cover administrative costs. Typically, the PACs are staffed by company lobbyists and distribute campaign contributions in line with the company's lobbying agenda.
Recent US supreme court rulings have transformed the regulatory landscape for corporations seeking to bring their influence to bear. President Barack Obama warned in a state of the union address, "I believe [the rulings] will open the floodgates for special interests - including foreign corporations - to spend without limit in our elections."
PAC activity is often overlooked because there are tight caps on money-flows into and out of PACs. For example, even the most active Britain Inc-linked PAC, sponsored by BAE, has only released $609,750 in the 2012 election race, of which 61% has gone to Republican candidates. And the money is well targeted: 14 of the 21-strong Congressional armed services subcommittee on readiness, for example, received money from BAE's PAC.
Other high-profile donors include Experian chief executive Don Robert, who contributed to the credit check group's 78% Republican-leaning PAC; BP chief executive Bob Dudley, who gives to the oil major's 71% Republican-leaning PAC; and former AstraZeneca chief executive David Brennan, who, until he resigned in April, gave to the group's 54% Republican-leaning PAC.
Few PACs linked to FTSE 100 firms have given directly to presidential candidates, but one exception is Citizens Financial, a committee backed by the US banking subsidiary of Royal Bank of Scotland. Despite RBS being 84% owned by the UK taxpayer, its PAC has channelled $2,500 to Mitt Romney.
Whatever the eccentricities of the PAC system, it has ensured that much corporate spending has remained transparent and comparatively small scale for many years. But the landscape changed radically two years ago, largely as a consequence of the controversial Supreme Court ruling, Citizens United v FEC, that concluded a corporation's first amendment right to freedom of speech trumped rules seeking to check the influence of big business.
This opened the door for companies or trade associations to spend more freely on publicity campaigns attacking, or supporting, policies associated with candidates. Though the law still prohibits businesses from giving directly from shareholder funds to a candidate's official war chest in federal elections, a way of working around that ban has effectively been established in law.
One example cited is the American Petroleum Institute (API) which fund TV advertising against legislators who support energy policies its corporate backers disapprove of. The API funded an advert targeting Missouri Democrat senator Claire McCaskill. It reportedly stated that her opposition to oil subsidies would raise petrol prices. Members of the API include BP, and the oil group's top US executive, Lamar McKay, sits as a director of the trade body.
Next week's Diageo annual general meeting presents investors with an opportunity to take a stand. As one of the few FTSE 100 companies both to sponsor a PAC and make direct donations in some US state elections, the company will ask shareholders at their annual meeting to support a routine resolution authorising political donations in the EU. It is unlikely to face much institutional investor resistance.