United Kingdom Prime Minister David Cameron admits he and his wife owned shares in an offshore trust set up by his late father, before selling them for £30,000 in 2010.
Mr Cameron has faced questions over Blairmore Holdings, an offshore company set up by his late father Ian.
He told the UK's ITV News he did not have "anything to hide" and had paid all UK taxes due on the profits he made from the sale of the shares.
The BBC understands the PM will publish his tax returns, possibly next week.
Leaked documents revealed Ian Cameron was a client of Panamanian law firm Mossack Fonseca and used one of the most secretive - albeit lawful - tools of the offshore trade after he helped set up a fund for investors.
He was a director of Blairmore Holdings Inc which, until 2006, used "bearer shares" to protect its clients' privacy.
'Difficult few days'
Mr Cameron told ITV News: "I don't have anything to hide. I'm proud of my dad and what he did and the business he established... I can't bear to see his name being dragged through the mud."
He said it had been a "difficult few days, reading criticisms of my father and his business practices - my dad, a man I love and admire and miss every day".
He said much criticism was based on a "fundamental misconception" that Blairmore Investment was set up to avoid tax.
"It wasn't. It was set up after exchange controls went, so that people who wanted to invest in dollar denominated shares and companies could do so, and there are many other, thousands of other unit trusts set up in this way," he said.
He said it was "properly audited" and reported to the Inland Revenue every year. Anyone who bought units in it was subject to capital gains tax when shares were sold, he said.
Mr Cameron said that, as the son of a stockbroker, he had owned stocks and shares in the past but sold them in 2010 shortly before he became prime minister.
"I didn't want to anyone to say you've got other agendas or vested interests," he said.
"Samantha and I had a joint account and we owned 5000 units in Blairmore investment trust which we sold in January 2010, that was worth something like £30,000.
He added: "I paid income tax on the dividends but there was a profit on it but that was less than the capital gains tax allowance, so I didn't pay capital gains tax, but it was subject to all the UK taxes in all the normal ways."
Downing Street said Mr and Mrs Cameron bought their holding in April 1997 for £12,497 and sold it in January 2010 for £31,500. That year the personal allowance before capital gains tax was paid was £10,100 per person.
On Wednesday, Downing Street issued a statement saying Mr Cameron, his wife and children do not benefit from offshore funds - following a day of questions from the media about whether his family retains an interest in the fund.
On Twitter, UK Labour MP John Mann accused Mr Cameron of having "covered up and misled".
"How he got his shares is irrelevant. He has no choice but to resign," he posted.