British Prime Minister David Cameron has acknowledged he once had a stake in his late father's offshore trust, in an interview with ITV News.

Cameron said he had owned shares in the Panamanian trust, Blairmore, but had sold them in 2010, before becoming prime minister.

"We owned 5000 units in Blairmore Investment Trust, which we sold in January 2010. That was worth something like STG30,000 ($A55,750)", he said.

"I paid income tax on the dividends. There was a profit on it but it was less than the capital gains tax allowance so I didn't pay capital gains tax," he added.

Cameron's late father, Ian, was among tens of thousands of people named in leaked documents from Panama law firm Mossack Fonseca which showed how the world's rich and powerful are able to conceal wealth and avoid taxes.

In a statement, a spokesman for Cameron told Reuters that the prime minister, his wife and their children did not benefit from any offshore funds at present.

On Wednesday a spokesman for Cameron said: "There are no offshore funds or trusts which the prime minister, Mrs Cameron or their children will benefit from in future."