LONDON - Prime Minister David Cameron said Tuesday that he had no personal offshore funds and defended his record on tackling tax avoidance, after the so-called Panama Papers raised questions about his family's financial affairs.

A massive leak of documents from Panamanian law firm Mossack Fonseca revealed how an investment fund co-founded by Cameron's late father, Ian Cameron, avoided paying taxes in Britain for 30 years by basing itself in the Bahamas.

Faced with calls by the opposition Labour party for an investigation into all those implicated in the leak, including his family, Cameron said that his wealth consisted of his salary, some savings and a house. "I own no shares, no offshore trusts, no offshore funds, nothing like that," Cameron said.

The Conservative leader said nothing about his family's potential offshore holdings, an issue that his office had previously said was a "private matter".

The revelations about his father are embarrassing for Cameron, who has sought to lead international efforts to improve financial transparency and whose government hosts an anti-corruption summit next month.

He insisted that "no prime minister has done more" to tackle tax evasion and aggressive tax avoidance, and said British authorities would look into the Panama leaks.

However, campaigners called for more action to tackle secretive company ownership in British overseas territories such as the Cayman Islands and British Virgin Islands.

Labour leader Jeremy Corbyn raised the prospect of taking control of the territories if they did not act.

Ian Cameron helped found Blairmore Holdings Inc in the Bahamas in the early 1980s and was reportedly one of five UK-based directors until shortly before his death in 2010.

His offshore details were public knowledge but the leaked documents revealed that the investment fund hired local residents to sign its paperwork to avoid paying tax in Britain.

"In 30 years, Blairmore has never paid a penny of tax in the UK on its profits," said The Guardian newspaper, which has seen the leaked documents along with the BBC.

There is no suggestion that the fund acted illegally or that the family did not pay tax on any repatriated assets.

But Corbyn called for an independent investigation and said: "I think the prime minister, in his own interest, ought to tell us exactly what's been going on."

He demanded the government "stop pussyfooting around on tax dodging", saying: "There cannot be one set of tax rules for the wealthy elite and another for the rest of us."

Cameron's government has recovered £2 billion (2.49 billion euros, $2.83 billion) from offshore tax evaders since 2010 and introduced a range of measures to clamp down on evasion, officials said.

Meanwhile, the state prosecutor's office in Panama said Monday it will launch an investigation into revelations contained in a massive data leak of a law firm that created offshore companies for the world's rich and powerful.

"The facts described in national and international communication media publications under the term 'Panama Papers' will be the subject of criminal investigation," the office said in a statement.

The probe will aim to establish what crimes might have taken place and who committed them, as well as identifying possible financial damages, it said.

The law firm involved, Mossack Fonseca, says the leak of 11.5 million documents from its servers was the result of a "limited hack," suggesting it believed an outside party was responsible.

One of its founders, Ramon Fonseca, told AFP the leak was an attack on Panama itself, which is dependent on its financial services sector.

Panama's president, Juan Carlos Varela, said his country would cooperate with "whatever government and whatever investigation" resulted from the scandal. But he also vowed to "defend the image of our country," which had been making progress in trying to lose a reputation as a hub for money laundering and other shady transactions.

Offshore entities, of themselves, are not illegal. But they can be used to launder money or hide assets from tax authorities in other countries.