• Government officials and their families and associates in Azerbaijan, Russia, Canada, Pakistan, the Philippines, Thailand, Canada, Mongolia and other countries have embraced the use of covert companies and bank accounts.
• The mega-rich use complex offshore structures to own mansions, yachts, art masterpieces and other assets, gaining tax advantages and anonymity not available to average people.
• Many of the world’s top’s banks – including UBS, Clariden and Deutsche Bank – have aggressively worked to provide their customers with secrecy-cloaked companies in the British Virgin Islands and other offshore hideaways.
• A well-paid industry of accountants, middlemen and other operatives has helped offshore patrons shroud their identities and business interests, providing shelter in many cases to money laundering or other misconduct.
• Ponzi schemers and other large-scale fraudsters routinely use offshore havens to pull off their shell games and move their ill-gotten gains.

Millions of internal records have leaked from Britain’s offshore financial industry, exposing for the first time the identities of thousands of holders of anonymous wealth from around the world, from presidents to plutocrats, the daughter of a notorious dictator and a British millionaire accused of concealing assets from his ex-wife.

Sample offshore owners named in the leaked files include:

• Jean-Jacques Augier, François Hollande’s 2012 election campaign co-treasurer, launched a Caymans-based distributor in China with a 25% partner in a BVI company. Augier says his partner was Xi Shu, a Chinese businessman.

• Mongolia’s former finance minister. Bayartsogt Sangajav set up “Legend Plus Capital Ltd” with a Swiss bank account, while he served as finance minister of the impoverished state from 2008 to 2012. He says it was “a mistake” not to declare it, and says “I probably should consider resigning from my position”.

• The president of Azerbaijan and his family. A local construction magnate, Hassan Gozal, controls entities set up in the names of President Ilham Aliyev’s two daughters.

• The wife of Russia’s deputy prime minister. Olga Shuvalova’s husband, businessman and politician Igor Shuvalov, has denied allegations of wrongdoing about her offshore interests.

•A senator’s husband in Canada. Lawyer Tony Merchant deposited more than US$800,000 into an offshore trust.

He paid fees in cash and ordered written communication to be “kept to a minimum”.

• A dictator’s child in the Philippines: Maria Imelda Marcos Manotoc, a provincial governor, is the eldest daughter of former President Ferdinand Marcos, notorious for corruption.

• Spain’s wealthiest art collector, Baroness Carmen Thyssen-Bornemisza, a former beauty queen and widow of a Thyssen steel billionaire, who uses offshore entities to buy pictures.

• US: Offshore clients include Denise Rich, ex-wife of notorious oil trader Marc Rich, who was controversially pardoned by President Clinton on tax evasion charges. She put $144m into the Dry Trust, set up in the Cook Islands.

It is estimated that more than $20tn acquired by wealthy individuals could lie in offshore accounts. The UK-controlled BVI has been the most successful among the mushrooming secrecy havens that cater for them.

The Caribbean micro-state has incorporated more than a million such offshore entities since it began marketing itself worldwide in the 1980s. Owners’ true identities are never revealed.

Even the island’s official financial regulators normally have no idea who is behind them.

The British Foreign Office depends on the BVI’s company licensing revenueto subsidise this residual outpost of empire, while lawyers and accountants in the City of London benefit from a lucrative trade as intermediaries.

They claim the tax-free offshore companies provide legitimate privacy. Neil Smith, the financial secretary of the autonomous local administration in the BVI’s capital Tortola, told the Guardian it was very inaccurate to claim the island “harbours the ethically challenged”.

He said: “Our legislation provides a more hostile environment for illegality than most jurisdictions”.

Smith added that in “rare instances …where the BVI was implicated in illegal activity by association or otherwise, we responded swiftly and decisively”.

The Guardian and ICIJ’s Offshore Secrets series last year exposed how UK property empires have been built up by, among others, Russian oligarchs, fraudsters and tax avoiders, using BVI companies behind a screen of sham directors.

Such so-called “nominees”, Britons giving far-flung addresses on Nevis in the Caribbean, Dubai or the Seychelles, are simply renting out their names for the real owners to hide behind.

The whistleblowing group WikiLeaks caused a storm of controversy in 2010 when it was able to download almost two gigabytes of leaked US military and diplomatic files.

The new BVI data, by contrast, contains more than 200 gigabytes, covering more than a decade of financial information about the global transactions of BVI private incorporation agencies. It also includes data on their offshoots in Singapore, Hong Kong and the Cook Islands in the Pacific.