An open letter sent to King Charles by the Tax Justice Network and published in the Guardian warns the King ahead of his coronation of the "heavy financial and human costs" inflicted on "ordinary people in the UK, the Commonwealth, and around the world by the British tax havens over which King Charles is sovereign".

"The financial regulations of Your Majesty's jurisdictions," Tax Justice Network chief executive Alex Cobham said in the statement, "pose the biggest non-violent threat in the world to human rights."

He urged King Charles to let his voice "be heard in this global discussion that will echo throughout history".

The UK, the Crown Dependencies and the British Overseas Territories are collectively responsible for facilitating nearly 40% of the tax revenue losses that countries around the world suffer annually to profit shifting by multinational corporations and to offshore tax evasion by primarily wealthy and powerful individuals. 

"Our latest estimates," the Tax Justice Network states in the letter, "put the sum of this tax loss imposed upon the world by British tax havens at over US$189 billion a year, which is more than three times the humanitarian aid budget the UN requested for this year".

The UK also "suffers from the lose-lose game of tax havenry", the open letter argued: "We estimate the UK itself loses at least US$52 billion in tax annually to global tax abuse, which is equivalent to losing the annual wages of over 1 million NHS nurses every year to multinational corporations and wealthy individuals underpaying tax in the UK."

Referring back to the King's comments in his first Christmas message on the "great anxiety and hardship" of those struggling to "pay their bills and keep their families fed and warm", the Tax Justice Network further wrote: "It is difficult in this context of current economic hardship to understand why Your Majesty's Treasury is leaving the option to recover £2.5 billion in tax from corporate tax abusers on the table and instead opting to require millions of hard working people to pay more tax on their incomes under the frozen income tax personal allowances."

While the Tax Justice Network "commended the example made by the King by committing to voluntarily pay income tax, which the late Queen had also done" it also "invited King Charles to set a further example by encouraging his enterprises to seek the Fair Tax Mark accreditation, a British-run international accreditation scheme considered to be "the gold standard of responsible tax conduct" for businesses and organisations."

"Bringing full financial and tax transparency to the monarchy offers a path for Your Majesty to provide a powerful impetus for good," the letter concluded.