Christian Aid has welcomed David Cameron's letter to the UK's Crown Dependencies and Overseas Territories reiterating the need to tackle fraud and tax evasion.
In the letter, the Prime Minister speaks of his desire for the UK to become a world leader in tax transparency, and work together with the territories in raising standards globally.
Specifically, Mr Cameron says tax havens must be clear about the ownership of the companies they host. He expressed his strong support for public access to a central company register, saying it was "key" to improving transparency in this area and meeting the "urgent" challenges of illicit finance and tax evasion.
"It will shed light on those who have provided false information, helping to tackle crime where it occurs and deterring people from providing this false information in the first place," he said.
"And it will help reduce the cost of investigations for tax and law enforcement authorities here and overseas, particularly in developing countries, by making information more easily available to them at the very start of an investigation."
The Crown Dependencies are Jersey, Guernsey and the Isle of Man, while the Overseas Territories include the British Virgin Islands, the Cayman Islands, Bermuda, Anguilla, and the Turks and Caicos.
Christian Aid has welcomed the Prime Minister's recommendation, saying it will help bring criminals who use secretly-owned companies to commit tax evasion, corruption and money laundering, to justice.
With a high proportion of direct investment in developing countries being channelled through the islands, Barry Johnston, Christian Aid's senior UK political adviser, said he was "extremely pleased" by the letter's call for a public register.
"Mr Cameron has already led the way on this issue, by committing the UK to introduce its own public register of the millions of people who own companies in this country," he said.
"He has since encouraged fellow European Union member countries to follow suit and today he is absolutely right to urge the Crown Dependencies and Overseas Territories to do the same.
"If these territories want to shake off the label of 'tax haven', then now is the time for them to do it."