The data includes information about companies, trusts, foundations and funds incorporated in 21 tax havens, from Hong Kong to Nevada in the US, and links to people in more than 200 countries and territories, ICIJ says.

Users will be able to search through the interactive database which will include, when available, Mossack Fonseca’s internal records of the company’s true owners. It will build on ICIJ’s existing data store of some 100,000 offshore trusts and funds based in the British Virgin Islands, the Cayman Islands, Cook Islands and Singapore, which formed part of an earlier 2013 offshore leaks investigation.

ICIJ describes the move as ‘a careful release of basic corporate information’, and says it will not be releasing personal data en masse, but rather focusing on select and limited information which it says is in the public interest. The database will not include records of bank accounts and financial transactions, emails and other correspondence, passports and telephone numbers.

Separately, Oxfam  has co-ordinated publication of  a letter signed by more than 300 leading economists from 30 countries , who have written to world leaders warning there is no economic justification for allowing tax havens and urging them to lift the veil on offshore secrecy.

 Signatories include Thomas Piketty, author of best-selling 'Capital in the Twenty-First Century', Angus Deaton, the 2015 Nobel Prize-winner for economics, and 47 professors from British universities including Oxford and the London School of Economics, plus international experts.

The economists state: ‘Territories allowing assets to be hidden in shell companies or which encourage profits to be booked by companies that do no business there are distorting the working of the global economy.’

To counter this, they are urging governments to agree new global rules requiring companies to publicly report taxable activities in every country they operate, and to ensure all territories publicly disclose information about the real owners of companies and trusts.

Jeffrey Sachs, director of Columbia University's Earth Institute and an adviser to UN secretary general Ban Ki-moon, said: ‘These havens are the deliberate choice of major governments, especially the UK and the US, in partnership with major financial, accounting, and legal institutions that move the money. 

‘We didn't need the Panama Papers to know that global tax corruption through the havens is rampant, but we can say that this abusive global system needs to be brought to a rapid end. That is what is meant by good governance under the global commitment to sustainable development.’

The letter comes ahead of the UK government's first global anti-corruption conference and summit to be held in London on May 11 and 12, with politicians from 40 countries as well as World Bank and IMF representatives expected to attend.

In its pre-summit comments, the UK government said: ‘We are in discussions with the overseas territories and crown dependencies with major financial centres about their attendance, and expect a number to join the summit.’

The ICIJ Panama Papers database will be published at 7pm on May 9

Details of the UK anti-corruption summit are here

The full list of signatories to Oxfam’s letter about offshore taxation is here: Full list of signatories to Oxfam letter