David Cameron's father ran a network of offshore investment funds to help build the family fortune that paid for the prime minister's inheritance, the Guardian can reveal.
Though entirely legal, the funds were set up in tax havens such as Panama City and Geneva, and explicitly boasted of their ability to remain outside UK tax jurisdiction.
At the time of his death in late 2010, Ian Cameron left a fortune of £2.74m in his will, from which David Cameron received the sum of £300,000.
Cameron and other cabinet members have recently suggested that they would be willing to disclose their personal tax filings amid growing scrutiny following the budget, but this would only shed light on annual sources of income rather than accumulated wealth or inheritance.
The structure employed by Cameron senior is now commonplace among modern hedge funds, which argue that offshore status can help attract international investors. UK residents would ordinarily have to pay tax on any profits they repatriated, and there is nothing to suggest the Camerons did not.
Nevertheless, the dramatic growth of such offshore financial activity has raised concerns that national tax authorities are struggling to pin down the world's super-rich.
Ian Cameron took advantage of a new climate of investment after all capital controls were abolished in 1979, making it legal to take any sum of money out of the country without it being taxed or controlled by the UK government.