Prime Minister David Cameron and his family do not benefit from any offshore funds, his spokesman said on Tuesday, after the British leader came under pressure over his late father's inclusion in the "Panama Papers" revelations over tax havens.
During a visit to a business in central England on Tuesday, Cameron said he did not own any shares or have any offshore funds but did not answer a question on whether he or his family had benefited from offshore investment funds set up by his father. On Monday, his spokeswoman had said it was a "private matter".
In a statement on Tuesday, a spokesman for Cameron said: "To be clear, the prime minister, his wife and their children do not benefit from any offshore funds." He did not say whether they had benefited in the past.
"The prime minister owns no shares ... Mrs Cameron owns a small number of shares connected to her father's land, which she declares on her tax return."
The leader of Britain's main opposition party urged the government to tackle tax havens, accusing Cameron of allowing "the super rich elite" to dodge taxes.
Leaked documents from the Panamanian law firm Mossack Fonseca have provided evidence of how the world's rich and powerful used secretive offshore company structures to stash their wealth.
The documents named Cameron's late father Ian and members of his Conservative Party among the list of the firm's clients.
The government has promised to investigate the leaked data but opposition Labour leader Jeremy Corbyn called for more to be done, including setting up an independent investigation.
"There cannot be one set of tax rules for the wealthy elite and another for the rest of us," Corbyn said at the launch of Labour's campaign for local elections next month.
"The unfairness and abuse must stop ... no more lip service, the richest must pay their way."
Corbyn said Britain had a "huge responsibility" as many tax havens are British overseas territories, such as the British Virgin Islands and Cayman Islands, or crown dependencies, such as Jersey or the Isle of Man.
When Britain hosted a G8 summit in 2013, Cameron put tackling tax avoidance at the heart of the agenda. Some of Britain's former colonies increasingly rely on revenues from shell companies and trusts that often hide wealth.
Three years later, some opposition lawmakers say the release of the "Panama Papers" shows the battle is far from won and are demanding that Cameron exert more control over Britain's overseas territories, most of which are self-governing.
According to media that have seen Mossack Fonseca's files, more than half of the 200,000 companies set up by the firm were registered in the British Virgin Islands, where details of ownership do not have to be filed with the authorities.
The head of the secretariat of the Global Forum on Transparency and Exchange of Information for Tax Purposes, Monica Bhatia, said the British Virgin Islands had improved transparency over the last five years, in contrast to Panama.
Dominic Grieve, a former attorney general and Conservative chair of parliament's Intelligence and Security Committee, said preventing overseas territories from running their own financial services would push crime elsewhere.
"The government has a responsibility towards encouraging overseas territories to find legitimate ways of economic development, and the financial sector is undoubtedly such a legitimate method," he told BBC radio, adding that people only used tax havens if their own systems were "onerous".
"The best way of ensuring that ... people do not want to go to the BVI is to provide the right environment domestically."