A Christian movement to end poverty has spoken out against tax evasion by wealthy people.

Micah Challenge is calling upon church leaders to hold the super-rich to account after a report by the Tax Justice Network suggested that up to $20trillion was being siphoned off by the world's wealthiest people into tax havens.

The movement says that Jesus would have hit out at such excessive greed, especially at a time when millions remain in extreme poverty and without access to basic health care.

The campaigners are urging churches the world over to raise their concerns with politicians.

"Once again the poor are paying the price of the greed of the wealthiest," said Head of Campaigns Amanda Jackson.

"These figures are horrifying and should make us angry, just as Jesus was angered by greed.

"The money being siphoned off to tax havens is more than the American and Japanese GDPs put together. Yet millions of the world's poorest are suffering. It is so wrong."

The report, The Price of Offshore Revisited, has been compiled by James Henry, tax haven expert and former chief economist at consultancy McKinsey.

He estimates that at least £13trillion ($20 trillion) has leaked out of scores of countries into secretive jurisdictions such as Switzerland and the Cayman Islands with the help of private banks, which vie to attract the assets of so-called high net-worth individuals.

London and some US states do not escape criticism for handling assets which could be used to reduce national debts.

Micah Challenge is backing the Exposed2013 campaign to shed light on corruption. The campaign, which launches in October, will petition the G20 nations to support a full and automatic exchange of tax information.

G20 nations will also be reminded of their promise to tackle banking secrecy and tax avoidance - something Micah Challange says could help the world's poorest.

Mrs Jackson added: "The Bible urges us to speak up for the poor and for those without a voice.

"Micah Challenge supports the call by Tax Justice Network for governments to act."