The letter also spells out the financial costs of refusing to make the commitment, specifically the fact that the Cook Islands is a signatory to the Cotonou agreement under which it stands to benefit to the tune of $6m a year for 15 years from the EU - but only if it maintains international standards of financial supervision.

Commenting, International Tax and Investment Organisation (ITIO) spokesperson Ben Coleman said, "It will be interesting to see whether the OECD accepts these reasonable conditions or whether it still demands that small states have to make changes more quickly than the OECD's own offshore centres of Switzerland and Luxembourg, which will have the effect of advancing OECD members' own interests at the expense of small countries."

"It is manifestly unfair to force small states to do anything before Switzerland and Luxembourg. All countries should move together, taking the same steps at the same time."

The ITIO is a grouping of small and developing economies (SDEs) set up in March 2001 to help SDEs respond to global tax and investment challenges. It explicitly considers the development implications of these challenges. The ITIO currently comprises Anguilla, Antigua and Barbuda, Bahamas, Barbados, Belize, British Virgin Islands, Cayman Islands, Cook Islands, Malaysia, St Kitts & Nevis, St Lucia, Turks & Caicos and Vanuatu. The Commonwealth Secretariat, Pacific Islands Forum Secretariat and CARICOM Secretariat have observer status.

The four OECD member countries who have refused to sign up to the OECD's project (Switzerland, Luxembourg, Belgium and Portugal) include the principal onshore competitors for the offshore world, and account for many of the tax neutral structures run onshore within the OECD. Offshore centres are concerned that if they are not obliged to adhere to the same standards as offshore centres, business will just migrate to these OECD members, which raises further doubts about the fairness of the process.