Non-domiciled people avoid £1bn of tax through their privileged tax status, according to the former Inland Revenue’s internal research.

According to documents released to Accountancy Age under the Freedom of Information Act, 77,000 individuals pay £5bn in UK taxes. The issue of non-domiciliaries – who pay tax on UK income, but not foreign income if it is not remitted to the UK – has long troubled anti-avoidance campaigners, including Gordon Brown.

The loophole has been used by some rich and famous overseas visitors, but principally by investment bankers. A substantial number of professional footballers also exploit the rules.

Though Brown continues to pledge to keep the policy under review, he has never launched a clampdown. The lower than expected avoidance figure may explain why the government has not pursued the issue more vigorously.

But tax advisers said the figure was almost certainly higher. Mike Warburton of Grant Thornton said: ‘There is no requirement for non-doms to ever disclose anything about their foreign investments.’ He added that he would be surprised if the tax avoided was less than £5bn.