The family of Pakistani Prime Minister Nawaz Sharif was defiant Monday, defending their ownership of offshore companies after they were named in the Panama Papers, one of the biggest leaks in history.

The leak, comprising 11.5 million documents from Panama-based law firm Mossack Fonseca, shows how some of the world's most powerful people have secreted away their money in offshore jurisdictions.

Among those named are three of Sharif's four children - Maryam, who has been tipped to be his political successor; Hasan and Hussain, with the records showing they owned London real estate through offshore companies administrated by the firm.

"Nawaz Sharif does not own any company but having companies in the name of his children also raises questions," Umar Cheema of the independent Center for Investigative Reporting in Pakistan (CIRP) told AFP.

The CIRP is partnered with the Investigative Consortium of Independent Journalists (ICIJ), which spent months poring over the documents ahead of Sunday's online release.

"There are more than 200 Pakistanis which our report has identified, and they include lawyers, lawmakers and some people from the judiciary," he said.

Opposition leader Imran Khan issued a swift call for action against Sharif after the release.

"Our stance vindicated again as Sharif's wealth stashed abroad exposed," he tweeted, adding the country's accountability watchdog, tax authorities and election commission "must take action". But Sharif's son Hussain told the country's largest private broadcaster Geo that his family had done "nothing wrong".

"Those apartments are ours and those offshore companies are also ours," he said in comments aired by the channel Monday. "There is nothing wrong with it and I have never concealed them, nor do I need to do that.

"It is according to British law and laws of other countries that it is a legal way to avoid unnecessary tax via offshore companies."

He left Pakistan in 1992, he added, and therefore is not resident, adding Pakistani tax law "says that if you are not staying in Pakistan for more than 138 days, then you are not required to declare your assets".

Regarding Khan's call for the National Accountability Bureau (NAB) to investigate, he said "we voluntarily present ourselves before it or any other judicial and investigative institution in Pakistan".

And he issued one final dig at Khan, calling on him to provide "proof that the Prime Minister has not declared his assets". "If he is successful in that then we are ready to accept our fault and undergo punishment," he said.

Nawaz Sharif's office has not yet responded to requests for comment by AFP.

Ali Nadir, a financial analyst, said the use of offshore companies was in many cases legitimate. But, he added: "I believe political and business leaders will be hard pressed to take the privacy defence given the worldwide move towards a better track of money, tax evasion, laundering and corruption.

"This may also start more locally focused probes as there are likely to be disclosure issues."

The Panama Papers have whipped a storm of controversy over off-shore wealth, ensnaring political leaders, sports figures and underworld members across the globe in a snowballing scandal

Source: KUNA