The corporate tax rate paid by leading British companies has fallen for the fourth year in a row, according to new research.
The report studied the value of a company's global taxes charged as a percentage of global profits, to produce an "effective tax rate".
The increasing international nature of the FTSE 100 means companies are generating greater profits overseas, allowing them to take advantage of lower tax rates abroad, said UHY Hacker Young.
Roy Maugham, head of the group's tax department, said: "Companies have a duty to their shareholders to keep costs low, and tax payments are a major cost.
"Companies are always exploring ways to make their tax payments as efficient as possible, which has helped chip away at their effective tax rates. Companies have also been given a hand by governments around the world.
"International competition to attract corporate tax revenues is as fierce as ever, with countries offering new enticements to businesses in the form of allowances, reliefs, or tax cuts. This means the overall FTSE 100 effective tax rate is pushed lower and lower."
Mr Maugham said the Government had made efforts to improve the attractiveness of the UK tax regime to business, such as reducing corporation tax, but he added that there was still "some way" to go.
More than 20 companies left the UK for tax reasons between 2007 and 2011, and very few have returned, the report added.
The claimed reduced rate of tax paid by top firms comes shortly after increased public awareness of the UK tax paid by major foreign multinationals.
Starbucks later announced a decision to give £10m annually to HM Revenue and Customs, which was slammed by critics as a "donation".
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