Cameron's initial reluctance to admit that he had benefited from the fund caused a furore, compounding his problems when he faces a huge political fight to persuade Britons to vote to stay in the European Union in a June 23 referendum.
The EU issue has split his Conservative Party, while the government has also been going through a tough patch over a senior minister's resignation, a u-turn on welfare cuts and accusations it is failing to protect Britain's steel industry.
After saying on Saturday that he could have handled the fallout from the Panama disclosures better, Cameron released a summary of his tax records for the past six years.
But any hope that this would draw a line under the row was short-lived, as the main Sunday newspapers zeroed in on a gift of 200,000 pounds ($282,500) Cameron received from his mother in 2011, suggesting it may be a way of avoiding inheritance tax.
A source at Cameron's Downing Street office said the suggestion was inaccurate.
Cameron is one of dozens of politicians around the world who have been hit by the leak of 11.5 million documents from the Panamanian law firm Mossack Fonseca which detail the creation of more than 200,000 companies in offshore tax havens.
- Reuters