Millions of confidential documents have been leaked from one of the world’s most secretive law firms, exposing how the rich and powerful have hidden their money.

Dictators and other heads of state have been accused of laundering money, avoiding sanctions and evading tax, according to the unprecedented cache of papers that show the inner workings of the law firm Mossack Fonseca, which is based in Panama.

The documents, dubbed "The Panama Papers", reveal links to 72 current or former heads of state and accuse some of them of having vested interests in their own banks and looting their own countries.

The data shows links to families and associates of some of the most powerful people in the world, including the former president of Egypt, Hosni Mubarak, the former Libyan leader, Muammar Gaddafi and the current president of Syria, Bashar al-Assad.

In the UK, several elected officials are involved with the law firm, including Baroness Pamela Sharples and the MP Michael Mates. They provided responses to the International Consortium of Investigative Journalists (ICIJ) and have either denied any financial benefit to the offshore companies or have completely denied the allegations of working with the law firm.

What are The Panama Papers?

Two close allies of the Russian President, Vladimir Putin, are linked to an alleged money-laundering ring thought to be worth $1billion, run by a bank based in St Petersburg, Bank Rossiya. One of those is the concert cellist Sergei Roldugin, who has known Mr Putin for many years, is godfather to Mr Putin’s daughter Maria, and introduced him to his now ex-wife Lyudmila. The bank in question has already faced sanctions from the European Union and the US after Russia's invasion of Crimea in 2014.

Whistleblowing controversies of the last decade Show all 12 1 /12 Whistleblowing controversies of the last decade Whistleblowing controversies of the last decade Edward Snowden NSA leak Articles in The Guardian revealed that the US and the UK spied on foreign leaders and diplomats at the 2009 G20 summit. Reuters Whistleblowing controversies of the last decade WikiLeaks' US diplomatic cables leak In 2009, former US soldier Chelsea Manning, downloaded hundreds of thousands of classified US Government documents, and passed them on to Jullian Assange's whistleblowing website WikiLeaks. Among the documents were 250,000 State Department diplomatic cables. One disclosed the close relationship between Russian President Vladimir Putin and then-Italian Prime Minister Silvio Berlusconi, the Guardian reported. Allegations included "lavish gifts", lucrative energy contracts and the use by Berlusconi of a "shadowy" Russian-speaking Italiango-between. Getty Images Whistleblowing controversies of the last decade WikiLeaks' US diplomatic cables leak WikiLeaks' US diplomatic cables leak: In a revelation which bruised the UK's 'special relationship' with the US, WikiLeaks published conversations by US commanders criticising Britain's military operations in Afghanistan. Getty Images Whistleblowing controversies of the last decade WikiLeaks' US diplomatic cables leak WikiLeaks' US diplomatic cables leak: One document disclosed startling levels of corruption in Afghanistan, including an incident involving the then vice-president, Ahmad Zia Massoud, who was reportedly stopped and questioned in Dubai when he flew into the emirate with $52m in cash. Getty Images Whistleblowing controversies of the last decade WikiLeaks' US diplomatic cables leak Another cable documented fears in Washington over Pakistan's nuclear weapons programme, in a volatile country with a strategic position in the Middle East. PA Whistleblowing controversies of the last decade WikiLeaks' US diplomatic cables leak Day four of the gradual drip of leaks exposed allegations that Russia and its intelligence agencies are using mafia bosses to carry out criminal operations, with one cable reporting that the relationship is so close that the country has become a "virtual mafia state". Getty Images Whistleblowing controversies of the last decade Edward Snowden NSA leak In 2013, The Guardian published classified US National Security Agency (NSA) documents, from a then anonymous whistleblower. Four days later he was exposed as former NSA contractor Edward Snowden. A month after the initial leak, the New York Times allegeded that the NSA received emails, video clips, photos, voice and video calls, social networking details, logins and other data held by a range of US internet firms. Whistleblowing controversies of the last decade Edward Snowden NSA leak Since Snowden revealed that the US had eavesdropped on German Chancellor Angela Merkel's phone, German-US relations have been strained. In May 2014, Mrs Merkel said still had significant differences with the United States over surveillance practices and that it was too soon to return to “business as usual," according to the New York Times. Getty Images Whistleblowing controversies of the last decade Edward Snowden NSA leak On 7 June, The Guardian published the Presidential Policy Directive 20, whcih included a list of potential targets for cyber-attacks by the US Government. Rex Features Whistleblowing controversies of the last decade Samy Kamkar iPhone and Android exposé In April 2014, hacker and researcher Samy Kamkar revealed that Android phones collect user location data every few seconds. Files are then transited to Google several times an hour. Getty Images Whistleblowing controversies of the last decade Samy Kamkar iPhone and Android exposé It is believed Apple and Google are using the data to better target adverts to smartphone users, according to The Guardian. Getty Images Whistleblowing controversies of the last decade Samy Kamkar iPhone and Android exposé The two companies have since justified the collection of data. In a letter to the US congress Apple confirmed it collected the data and said that, in order to be useful, "the databases [of tower and network locations] must be updated continuously". A Google spokesman told the Guardian Android phones explicitly asked to collect anonymous location data when users turned them on. Getty Images

The papers were initially leaked via the German newspaperSüddeutsche Zeitung to the ICIJ. Gerard Ryle, director of the ICIJ, who has been analysing the documents along with 107 media outlets across more than 70 countries, told the BBC: “I think the leak will prove to be probably the biggest blow the offshore world has ever taken because of the extent of the documents.” The leak will be the subject of a Panoramadocumentary tonight. The source of the leak remains unidentified.

Another accusation in the files is that the prime minister of Iceland, Sigmundur Gunnlaugsson, had an undeclared interest in the bailed-out banks in the country, hiding millions of dollars in Iceland’s banks via an opaque offshore company.

Iceland was one of the few countries following the 2008 financial crisis to jail several of its bankers, who were accused of taking excessive risk which led to the collapse of their economy.

Yet Mr Gunnlaugsson and his wife bought Wintris, an offshore company, in 2007 but did not declare an interest in the company when they entered parliament. The company was used to invest millions of inherited money. He then sold his 50 per cent stake in Wintris to his wife for 70 pence ($1) eight months later.

Mr Gunnlaugsson has faced calls for his resignation but has reportedly said he has done nothing illegal and his wife has not benefitted financially from the arrangement.

Offshore companies are often located in countries such as Panama and are subject to their own tax rules, often functioning as tax loopholes or requiring much lower taxes than in an investor’s home country.

The law firm documents additionally show how individuals could take out large amounts of cash without revealing who they are to the public. In one case, the firm acted on behalf of a man who pretended to be the owner of $1.8m so that the real owner could take out the money without revealing their identity.

The ICIJ has listed 140 politicians from more than 50 countries who are linked to offshore companies in 21 tax havens, including countries such as Argentina, Georgia, Iraq, Jordan, Qatar and Ukraine.

Mossack Fonseca said it has operated “beyond reproach” for 40 years and has never been acused or charged with criminal wrong-doing.