The hidden wealth of some of the world’s most prominent leaders, politicians and celebrities will be revealed by the leak of millions of documents showing the way the rich exploit secretive offshore tax regimes like Panama’s.

The Guardian, one of several newspapers working with global partners, said journalists from more than 80 countries have been reviewing 11.5 million files leaked from the database of Mossack Fonseca, the world’s fourth biggest offshore law firm.

The leak is one of the biggest ever – larger than the US diplomatic cables released by WikiLeaks in 2010, and the secret intelligence documents given to journalists by Edward Snowden in 2013.

A Maltese connection surfaced with energy minister Konrad Mizzi, who was already outed as having used a Panamanian shell company, Hearnville, to hide his beneficial ownership; the company is owned by the trustees of his New Zealand trust. He is the only EU minister to feature in the list, so far.

Downloadable Files Deed for Konrad Mizzi's Rotorua Trust



In a statement released late on Sunday night, Mizzi said that the Panama leaks have confirmed that his "version of events, including disclosure, were truthful".

"The Trust and related documents published have been made available to journalists from the very start and the structure was always intended as a family trust for assets and investments. Contrary to other hundreds of persons mentioned, these leaks make no reference to any funds held by me. This confirms my version of events from the very beginning; that is that there are no funds and bank accounts held by these structures."

Mizzi argued that the opening of a bank account was "part of the service that was offered" to him.

"Nevertheless, as a state of fact confirmed by the reports, I did not pursue this option and never opened any account either in Dubai, Panama or elsewhere. I also notified the establishment of the structure in my draft Ministerial Declaration of Assets submission for 2015," Mizzi said.

"Irrespective of all this, I will continue pursuing the tax investigation and an independent audit to further prove what I have been stating consistently from the beginning. The company in Panama will be closed soon after the tax investigation is concluded."

In his comments to the ICIJ, a law firm representing Mizzi said the Panama company Hearnville Inc. was acquired "to hold a London property" owned with his wife, Sai Mizzi Liang.

"The company, which the law firm said has no assets nor bank accounts, was owned by a family trust under an arrangement recommended by professional advisers. The trust was registered in New Zealand, where the law firm noted trustees 'are obliged to declare relevant information to the New Zealand tax authorities, who in turn will share this information with the Maltese tax authorities'. The firm also said Mizzi 'declared his interest in the Company and the Trust in his 2015 [sic] Ministerial Declaration of Assets at the first available opportunity.' Mizzi has asked Malta's tax authorities to audit his financial affairs and has said that he will close Hearnville once it is complete."

The documents published by the ICIJ confirm that Nexia BT, a Mossack Fonseca agent in Malta, acquired Hearnville Inc from ATC Administrators, for which Mizzi was its beneficial owner. Hearnville is owned by Orion Trustees of New Zealand, who manage his trust, Rotorua, whose beneficiaries are his wife and children.

Hearnville was incorporated in Mizzi's name on 2 July, 2015.

In his initial reaction, Opposition leader Simon Busuttil fired off a tweet telling Prime Minister Joseph Muscat it was "time to go".

@JosephMuscat_JM : if this is what you've been defending, it's time for you to go. pic.twitter.com/nhWnERCaTA — Simon Busuttil (@SimonBusuttil) April 3, 2016

Joseph Muscat said he will not sack Mizzi unless an audit from the Commissioner for Inland Revenue and an independent audit finds any money stashed away in the offshore company or some offshore account.

Leak of over 11.5 million files

Although using offshore structures is entirely legal, the global rich use such financial vehicles for reasons of inheritance and estate planning, or to stash away assets from tax authorities.

Panama law firm Mossack Fonseca is the world’s fourth biggest provider of offshore services, having for more than 300,000 companies.

It has already warned clients of the imminent ‘Panamaleaks’ revelations.

The records were obtained from an anonymous source by the German newspaper Süddeutsche Zeitung and shared by the International Consortium of Investigative Journalists (ICIJ) with the Guardian and the BBC.

370 reporters from 100 media organisations have spent a year analysing and verifying the documents.

The ‘Panama Papers’ reveal:

• Twelve national leaders, among 143 politicians, their families and close associates from around the world known to have been using offshore tax havens: they include Nawaz Sharif, Pakistan’s prime minister; Ayad Allawi, ex-interim prime minister and former vice-president of Iraq; Petro Poroshenko, president of Ukraine; Alaa Mubarak, son of Egypt’s former president; and the prime minister of Iceland, Sigmundur Davíð Gunnlaugsson.

• Six members of the UK’s House of Lords, three former Conservative MPs and dozens of donors to UK political parties have had offshore assets.

• The families of at least eight current and former members of China’s supreme ruling body, the politburo, have been found to have hidden wealth offshore.

The company has denied any wrongdoing. It says it has acted beyond reproach for 40 years and that it has had robust due diligence procedures.