LONDON (REUTERS) - Prime Minister David Cameron will press Britain's overseas tax havens to sign up to an international transparency treaty in London on Saturday, before he meets leaders of G8 economies to push for coordinated global action on tax avoidance and evasion.

He will ask 10 territories and self-governing regions, among the world's top tax havens, to sign the Multilateral Convention on Mutual Assistance in Tax Matters - an initiative led by the Organisation for Economic Cooperation and Development (OECD), a government statement released before next week's talks said.

Bermuda, one of Britain's territories, said on Thursday it had agreed to back the OECD treaty, which is signed by more than 50 countries and requires them to share information on individuals who hold bank accounts in their jurisdictions.

Mr Cameron is also seeking agreement from the British Virgin Islands, the Cayman Islands, Gibraltar, Anguilla, Montserrat, Turks and Caicos Islands, Jersey, Guernsey and the Isle of Man.

He said in an interview with the Guardian newspaper on Saturday he wanted to "sweep away" tax secrecy.

"We need to know more about who owns which company - beneficial ownership - because that is how a lot of people and a lot of companies avoid tax, using secretive companies in secretive locations," he said.

"The way to sweep away the secrecy and get to the bottom of tax avoidance and tax evasion and cracking down on corruption is to have a register of beneficial ownerships so the tax authorities can see who owns beneficially every company."

Global tax evasion could be costing more than US$3 trillion (S$3.8 trillion) a year according to researchers from Tax Justice Network while as much as US$32 trillion - twice the size of US gross domestic product - could be hidden by individuals in tax havens.

"Corruption is wrong. It starves the poor. It poisons the system. It saps the faith of people in progress. It wrecks the case for aid," Mr Cameron will say at the conference.