A Downing Street spokesperson said the Prime Minister nor his immediate family benefit from offshore funds.
Mr Cameron has been under scrutiny since it was revealed in a leak of documents from a Panama law firm that his late father Ian Cameron ran funds which avoided paying UK tax.
The Guardian newspaper, which was handed the documents held by firm Mossack Fonseca, said Mr Cameron's father avoided paying tax in Britain by hiring a small army of Bahamas residents - including a part-time bishop - to sign its paperwork.
Mr Cameron senior was a director of Blairmore Holdings Inc, which, until 2006, used unregistered "bearer shares" to protects its clients' privacy and have since been made illegal by his son.
His use of the firm to help shield investments from UK tax helped build up a significant legacy, part of which was inherited by the Prime Minister after his death in 2010.
David Cameron said on a visit to Birmingham today to give a speech on the EU that he does not own any shares.
He said: "I have a salary as prime minister and I have some savings, which I get some interest from, and I have a house, which we used to live in, which we now let out while we are living in Downing Street and that’s all I have.
"I own no shares, no offshore trusts, no offshore funds, nothing like that. And, so that, I think, is a very clear description."
This was followed by a statement from a No 10 spokesperson, who said: “To be clear, the Prime Minister, his wife and their children do not benefit from any offshore funds."
This may be an attempt to silence speculation that his family could benefit from money held in offshore holdings in the future.
The statement said: “The Prime Minister owns no shares.
“As has been previously reported, Mrs Cameron owns a small number of shares connected to her father’s land, which she declares on her tax return.”
The statement came as his counterpart in Iceland, Prime Minister Sigmundur David Gunnlaugsson resigned over his links to the Panamanian law firm.
He and his wife Anna Sigurlaug Palsdottir were found to have set up a company Wintris Inc. in the British Virgin Islands with the help of Mossack Fonseca.
Gunlaugsson is accused of a conflict of interest for failing to disclose his involvement in the company, which held interests in failed Icelandic banks that his government was responsible for overseeing.
He had been head of the centre-right Progressive Party and began his four-year term in 2013, five years after Iceland's financial collapse.